NOAA's National Centers for Environmental Information
Issued 13 June 2024
Please note that the values presented in this report are based on preliminary data. They will change when the final data are processed, but will not be replaced on these pages.
National Drought Highlights
- Based on the Palmer Drought Index, severe to extreme drought affected about 6% of the contiguous United States as of the end of May 2024, a decrease of about 3% from last month. About 5% of the contiguous U.S. fell in the severely to extremely wet categories.
- About 13% of the contiguous U.S. fell in the moderate to extreme drought categories (based on the Palmer Drought Index) at the end of May.
- On a broad scale, the 1980s and 1990s were characterized by unusual wetness with short periods of extensive droughts, the 1930s and 1950s were characterized by prolonged periods of extensive droughts with little wetness, and the first two decades of the 2000s saw extensive drought and extensive wetness (moderate to extreme drought graphic, severe to extreme drought graphic).
- A file containing the national monthly percent area severely dry and wet from 1900 to present is available for the severe to extreme and moderate to extreme categories.
- Historical temperature, precipitation, and Palmer drought data from 1895 to present for climate divisions, states, and regions in the contiguous U.S. are available at the Climate Division: Temperature-Precipitation-Drought Data page. These filenames begin with "climdiv".
- According to the weekly U.S. Drought Monitor (USDM), as of May 28, 2024, 12.55% of the contiguous U.S. (CONUS) (10.5% of the U.S. including Alaska, Hawaii, and Puerto Rico) was classified as experiencing moderate to exceptional (D1-D4) drought.
Detailed Drought Overview
The upper-level atmospheric circulation over North America during May 2024 was characterized by powerful short-wave troughs and closed lows during the first half of the month that congregated over the western and central states. During the last half of the month, the overall circulation alternated between a more westerly (or zonal) flow and a pattern with troughs collecting in the West and ridging occurring in the east. When averaged over the month, the circulation pattern was fairly zonal with a slight dip (trough) in the West, reflecting a significant departure from the long-term average circulation pattern. The troughs and closed lows dragged cold fronts and surface lows with them. There was enough Pacific moisture with some of them to give parts of the Pacific Northwest and northern Rockies a wetter-than-normal month, but most of the West ended up drier than normal. The fronts and surface lows tapped Gulf of Mexico and Atlantic moisture to spread above-normal precipitation across the Gulf Coast states, Mid-Mississippi Valley to Mid-Atlantic states, and northern Plains to Upper Midwest. They also triggered several rounds of severe weather across the Plains to East Coast. Monthly temperatures were cooler than average over much of the West, due to the influence of the upper-level troughs, and warmer than average from the Plains to East Coast.
Outside of the CONUS, troughing in the west extended across western Canada to Alaska, giving Alaska a near- to cooler-than-normal month with a mixed precipitation anomaly pattern. Ridging over Mexico extended across the Caribbean, giving Puerto Rico and the U.S. Virgin Islands a warmer-than-normal month with a mixed precipitation anomaly pattern. Anomalous troughing in the Pacific brought a Kona Low to Hawaii with heavy rains that gave the state a wetter-than-normal month.
The above-normal precipitation in the northern Plains to Midwest, Hawaii, and parts of the Pacific Northwest, central to southern Plains, and Mid-Mississippi Valley to the Mid-Atlantic contracted or reduced the intensity of drought and abnormal dryness compared to the end of April. But dry conditions in parts of the Pacific Northwest, western parts of the Plains, southern Texas, and much of the Florida peninsula resulted in expansion or intensification of drought and abnormal dryness. Drought contraction exceeded expansion with the USDM-based national moderate-to-exceptional drought footprint across the CONUS decreasing from 17.0% at the end of April to 12.6% at the end of May (from 14.2% to 10.5% for the 50 states and Puerto Rico).
According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 13.0% of the CONUS was in moderate to extreme drought at the end of May, which is less than the end of April.
Drought conditions at the end of May, as depicted on the May 28, 2024 USDM map, included the following core drought and abnormally dry areas:
- In the West, moderate (D1) to extreme (D3) drought covers about 20.3% of the Pacific Northwest, which is slightly more than last month, and moderate to exceptional (D4) drought affected about 30.3% of the Southwest (Four Corners states), which is about the same as last month. For the West as a whole, the percent area experiencing moderate to exceptional drought, according to USDM statistics, decreased from 20.6% at the end of April to 18.9% at the end of May. Based on the Palmer Drought Index, the drought area across the West as a whole decreased from 18.5% at the end of April (revised figures) to 16.5% at the end of May. Mountain snowpack (based on USDA SNOTEL SWE data) was mostly below normal for this time of year. Reservoir levels were near to above normal in most northern and central basins, with low reservoir levels in southern basins in the West and a few basins in the north.
- New Mexico set a new drought duration record at the end of May. According to USDM statistics, New Mexico has experienced moderate or worse drought for 345 weeks, beginning on October 24, 2017.
- In the Great Plains, moderate to extreme drought covered about 13.6% of the central to northern Plains, which is less than last month, and 36.5% of the southern Plains, which is also less than last month. The Lower Mississippi River Valley experienced a continued decrease in the drought area , going from 4.8% at the end of April to 0.5% at the end of May. Drought ended in Tennessee this month. Taken together, the southern Plains, Lower Mississippi Valley, and Tennessee (South region) saw moderate to extreme drought contract from 18.4% at the end of April to 15.8% at the end of May.
- Oklahoma set a new drought duration record at the end of May. According to USDM statistics, Oklahoma has experienced moderate or worse drought for 253 weeks, beginning on July 30, 2019.
- Severe to extreme drought ended in the Midwest, with moderate drought contracting to 0.8%. With drought ending in Iowa, this terminated a USDM drought duration record of 203 weeks, beginning on July 7, 2020 and ending on May 21, 2024. Missouri set a new drought duration record at the end of May. According to USDM statistics, Missouri has experienced moderate or worse drought for 101 weeks, beginning on June 28, 2022. The drought is effectively over in Missouri, with only 0.01% of the state in moderate drought as of May 28.
- Moderate to severe (D2) drought covered 6.7% of the Southeast, which is more than last month. The drought area is mostly in the Florida peninsula.
- Moderate to severe drought shrank to cover 8.2% of Hawaii.
- In the U.S.-Affiliated Pacific Islands (USAPI), 2 stations were abnormally dry, 2 were experiencing moderate drought, 1 was experiencing severe drought, and 4 had extreme drought conditions. This compares to 2 abnormally dry, 3 with moderate drought, 2 with severe drought, 1 with extreme drought, and 3 with exceptional drought at the end of April.
Palmer Drought Index
The Palmer drought indices measure the balance between moisture demand (evapotranspiration driven by temperature) and moisture supply (precipitation). The Palmer Z Index depicts moisture conditions for the current month, while the Palmer Hydrological Drought Index (PHDI) and Palmer Drought Severity Index (PDSI) depict the current month's cumulative moisture conditions integrated over the last several months.
While both the PDSI and PHDI indices show long-term moisture conditions, the PDSI depicts meteorological drought while the PHDI depicts hydrological drought. The PDSI map may show less severe and extensive drought (as well as wet spell conditions) in some parts of the country than the PHDI map because the meteorological conditions that produce drought and wet spell conditions are not as long-lasting as the hydrological impacts.
Used together, the Palmer Z Index and PHDI maps show that short-term drought occurred in the Southwest, western parts of the central Plains, in the Rio Grande Valley, across the Florida peninsula, and in parts of the Northeast, expanding or intensifying long-term drought and shrinking or reducing the intensity of long-term wet conditions (PHDI maps for May compared to April). Short-term wet conditions occurred across the northern Plains to Upper Midwest, along the Gulf of Mexico Coast, and from the Mid-Mississippi Valley to Mid-Atlantic states, contracting or reducing the intensity of long-term drought and expanding or intensifying long-term wet conditions.
Standardized Precipitation Index
The Standardized Precipitation Index (SPI) measures moisture supply. The SPI maps here show the spatial extent of anomalously wet and dry areas at time scales ranging from 1 month to 24 months.
The SPI maps illustrate how moisture conditions have varied considerably through time and space over the last two years. Dryness is evident across much of the West, especially southern parts, at 1- and 2-month time scales, and in parts of the Southwest and Pacific Northwest at 3 to 24 months. Western parts of the central Plains are dry at 1 to 3 months, with parts to much of the Rio Grande Valley dry at all time scales. Three parts of the Great Plains (northern, central, and southern) are dry at 24 months, with near normal or wet conditions separating the three dry sections. The southern half of the Florida peninsula is dry at 1- to 3-month time scales. A few parts of the East Coast are dry at 1, 2, and 24 months. Parts of the Mississippi, Ohio, and Tennessee Valleys are dry at 9- to 24-month time scales. Wet conditions dominate much of the CONUS east of the Rockies at 1-6 months, the Northeast at 3-24 months, and much of the West at 12-24 months.
Standardized Precipitation Evapotranspiration Index
The SPI measures water supply (precipitation), while the SPEI (Standardized Precipitation Evapotranspiration Index) measures the combination of water supply (precipitation) and water demand (evapotranspiration as computed from temperature). Warmer temperatures tend to increase evapotranspiration, which generally makes droughts more intense.
For the Northern Hemisphere, May marks the end of climatological spring, which is the season when days get longer, sun angle increases, and temperatures and evapotranspiration increase. During May 2024, temperatures were warmer than normal across the eastern and southern CONUS, with record warmth along the Gulf Coast. Evapotranspiration was unusually high, especially in those areas that were excessively hot and unusually dry. The 1-month SPEI values were more extreme (dry) than the corresponding SPI in southern and western Texas and in the Florida peninsula, where it was hot and dry. In much of the West, however, the May SPI was more extreme than the SPEI due to the anomalously cold temperatures. Even though temperatures were unusually warm across much of the CONUS for the last 3 to 6 months, precipitation was fairly evenly distributed or wet (except in a few areas) during this period, so the SPEI and SPI maps had similar magnitudes for most areas for much of this period (SPEI maps for the last 1, 3, 6, 12 months) (SPI maps for the last 1, 3, 6, 12 months).
The last 1 to 6 years have been unusually warm across much of the CONUS, especially in the South and West (state temperature rank maps for the last 1, 2, 3, 4, 5 years). Precipitation in the last 12 months has helped reduce deficits in many areas. But the last 2 years have been extremely dry in the Upper Mississippi Valley and parts of the Pacific Northwest, and the last 3 to 5 years have been quite dry in the West to Great Plains (state precipitation rank maps for the last 1, 2, 3, 4, 5 years). In the last 1 to 6 years, the SPEI is more extreme than the SPI in the Pacific Northwest but especially in the Southwest to Lower Mississippi Valley. In the western U.S., where drought has dominated for much of the last 20 years, the combination of excessive heat and dryness has resulted in more extreme SPEI values than SPI values in parts of the West for the last 2 to 6 years (SPEI maps for last 12, 24, 36, 48, 60, 72 months) (SPI maps for last 12, 24, 36, 48, 60, 72 months).
The 24-month SPEI for New Mexico is more extreme than the corresponding SPI, ranking second driest on record compared to the SPI which is barely in the top 10 driest category. The 24-month SPEI for several Texas and New Mexico sub-basins of the Rio Grande River is record dry where the corresponding SPI is not record dry or is even near average:
Regional Discussion
Rio Grande River Basin
During October 2023-May 2024, parts of the Rio Grande River Basin were wetter than normal, parts drier than normal, and parts near normal. But very dry and hot conditions of summer and early fall last year created significant precipitation deficits and expanded drought. The last two months (April and May 2024) were mostly drier than normal, with the basin having the 34th driest May in the 1895-2024 record, 19th driest April-May, 25th driest March-May (last 3 months), 45th driest December-May (last 6 months), and 13th driest June-May (last 12 months). Temperatures have also been anomalously warm — May ranked seventh hottest in the 130-year record, March-May was 11th warmest, December-May ranked fourth warmest, and June-May was the warmest such 12-month period. According to the USDM, 75.4% of the basin was in moderate to exceptional drought at the end of May, which is about the same as the 75.8% at the end of April. Based on the Palmer Drought Index, 88.8% of the basin was in moderate to extreme drought at the end of May, which is less than the end of April and less than the peak of 100% that occurred just last year and many times in the last 30 years, 1950s, and early 1900s.
Hawaii
May 2024 was wetter than normal across most of the main Hawaiian Islands. This resulted in wetter-than-normal conditions for the last 2 months. But some areas were still drier than normal at the 3- to 6-month time scales, especially across Molokai, Maui, Lanai, and the lee slopes (western half) of the Big Island. A mixed precipitation anomaly pattern was evident at the 12-month time scale, except across the Big Island where it was mostly drier than normal (precipitation anomaly maps for the last 1, 2, 3, 4, 6, 12, 60 months) (climate engine model percent of normal precipitation map for the last month).
Monthly streamflow was near to above normal across the main islands. Based on satellite analyses (stressed vegetation, drought stress, VHI), vegetation was stressed on parts of the Big Island, Molokai, and Maui.
Moderate to severe drought continued on the Big Island and Maui. The drought area in Hawaii decreased from 33.4% at the end of April to about 8.2% of the state on the May 28, 2024 USDM map.
Alaska
Alaska had a mixed precipitation anomaly pattern for May and most months for the last year, but some areas with persistent dryness include: the southern panhandle at 2- to 5-month time scales, the Cook Inlet to some interior regions at 2 to 8 months, some northern coastal locations at 1 to 2 months, and parts of the Aleutians at 1 to 12 months (low elevation station precipitation anomaly maps for the last 1, 2, 3, 4, 6, 12, 60 months) (high elevation SNOTEL station precipitation percentile maps for the last 1, 5, and 8 months) (SNOTEL basin and station percent of normal precipitation maps for the last 1, 2, 5, and 8 months) (climate division precipitation rank maps for the last 1, 3, 5, 6, and 12 months) (climate engine model percent of normal precipitation map for the last month) (Leaky Bucket model precipitation percentile map).
May temperatures averaged cooler than normal (1991-2020 normals) across the state. Some stations were near to warmer than normal at the 2-month time scale, with more warmer than normal at 3 to 4 months especially from the interior to northern and western regions. A mixed temperature anomaly pattern was evident at 5 months, with warmer-than-normal temperatures becoming dominant at 12 months. When temperatures are compared to the long-term (1925-2024) average, however, the anomalies were near average for May 2024 and predominantly warmer than average at longer time scales. This is due to a pronounced warming trend in recent decades (low elevation station temperature anomaly maps for the last 1, 2, 3, 4, 5, 12 months) (climate division temperature rank maps for the last 1, 3, 5, 6, and 12 months) (gridded temperature percentile maps for the last 1, 3, and 5 months) (Leaky Bucket model temperature percentile map).
Monthly streamflow was mostly near normal, with some below-normal stream levels. Snow has melted out of many areas, with the higher elevations and northern locations still having snow cover; snow water content (SWE) was below normal in the panhandle but near to above normal in the Southeast, Northwest Gulf, and Cook Inlet basins. Satellite observations of vegetative health (stressed vegetation, drought stress, VHI) revealed areas of lightly stressed vegetation, but no areas of significant stress. Satellite-based or modeled observations of groundwater and soil moisture (GRACE root zone and GRACE surface soil moisture; SPoRT estimates of soil moisture at four depths [0-10 cm, 10-40 cm, 40-100 cm, 100-200 cm]; Leaky Bucket modeled soil moisture) suggested some dryness was occurring in parts of the south and northeast, but the ground was still frozen in some areas; a more accurate determination will be made once the ground thaws.
Alaska was free of drought on the May 28, 2024 USDM map, although some abnormal dryness continued in the southern panhandle.
Puerto Rico and U.S. Virgin Islands
May 2024 was wetter than normal across most of Puerto Rico (PR) and the U.S. Virgin Islands (USVI). Wetter-than-normal conditions dominated the 2- to 8-month time periods. Drier-than-normal areas were evident at 8 to 12 months (radar-based precipitation anomaly estimates for the last 1, 2, 3, 4, 5, 6, 8, and 12 months) (low elevation station precipitation anomaly maps for the last 1, 3, 4, 12, 60 months) (climate engine model percent of normal precipitation map for the last month: PR and USVI, Caribbean and Gulf of Mexico region).
Temperatures were generally warmer than normal for May and much of the last 12 months (low elevation station precipitation anomaly maps for the last 1, 2, 3, 4, 12 months). Root zone analysis indicated that soil conditions were dry across the southern coast and parts of the northwestern coast of PR, with dryness more evident in the mid-level and deeper soil layers compared to shallower soil layers (root zone soil saturation fraction, SPoRT estimates of soil moisture at four depths [0-10 cm, 10-40 cm, 40-100 cm, 100-200 cm]). Satellite observations of vegetative health (stressed vegetation for PR and USVI, drought stress for PR and USVI, VHI for PR and USVI) revealed few if any areas of stressed vegetation. Monthly streamflow on PR showed near- to above-normal stream levels. In the USVI, groundwater levels generally rose during May, steadily increasing on St. Croix and rising, falling, then rising again before falling slightly on St. John and St. Thomas. The end-of-May groundwater level rose to the middle third of the recent historical record on St. Croix, but was in the upper third at St. John and St. Thomas.
In the USVI, abnormal dryness ended on St. Thomas, which makes the entire USVI free of drought and abnormal dryness. Abnormal dryness ended on PR, which makes the territory also free of drought and abnormal dryness on the May 28, 2024 USDM map.
CONUS State Precipitation Ranks
May 2024 was drier than normal across much of the West (especially the Southwest) and the Florida panhandle, and parts of the Plains, Midwest, and Northeast, with record dryness locally in the Southwest. Only four states had a precipitation rank in the driest third of the historical record for May. None ranked in the top ten driest category, but one came close — Arizona (12th driest). In other states, the precipitation was not low enough, or above-normal precipitation fell over parts of the states, to prevent them from ranking in the bottom third.
Parts of the CONUS have had very dry conditions at various times during the past 6 months, but the location of the dryness varied from month to month and some of the dry areas had wetter-than-normal conditions during intermittent months (low elevation station precipitation anomaly maps for the last 3, 5, and 6 months) (climate division precipitation rank maps for the last 3, 5, and 6 months) (gridded precipitation percentile maps for the last 3 and 5 months). Persistently dry areas include parts of the Plains (especially the Rio Grande Valley), West, and Florida. Those states that were dry experienced enough precipitation over other parts of the state to balance out the dryness. So, only 2 states ranked in the driest third of the 1895-2024 record for March-May and none were in the driest third of the historical record for January-May and December-May; no state ranked in the top 10 driest category for these three time scales.
June 2023-May 2024 was drier than normal across the Southwest to Gulf of Mexico coast, and parts of the Great Plains, Pacific Northwest, and Mississippi and Ohio Valleys. Only three states had a precipitation rank in the driest third of the historical record for June-May. None ranked in the top ten driest category, but one was in the bottom 20 category — New Mexico (17th driest). In other states, the precipitation was not low enough, or above-normal precipitation fell over parts of the states, to prevent them from ranking in the bottom third.
Agricultural Belts
During May 2024, the Primary Corn and Soybean agricultural belt was mostly warmer and wetter than normal. The month ranked as the 14th wettest and 20th warmest May, regionwide, in the 1895-2024 record.
March marks the beginning of the growing season for the Primary Corn and Soybean belt. March-May 2024 was warmer and mostly wetter than normal. The period ranked as the third warmest and 12st wettest March-May, regionwide, in the historical record.
According to the U.S. Department of Agriculture (USDA), as of May 28, 2024, drought affected approximately 8% of barley production, 5% of corn production, 5% of cotton production, 54% of sorghum production, 3% of soybean production, 3% of spring wheat production, 25% of winter wheat production, 7% of hay acreage, 12% of the cattle inventory, 8% of the milk cow inventory, and 10% of the sheep inventory. All of these (except for sorghum) are lower than they were last month.
Based on June 2 USDA statistics, 18% of the nation's winter wheat crop, 4% of the corn crop, 2% of the spring wheat crop, and 19% of the pasture and rangeland were in poor to very poor condition, and 15% of the nation's topsoil and 17% of the subsoil were short or very short of moisture (dry or very dry).
U.S.-Affiliated Pacific Islands
The NOAA National Weather Service (NWS) offices, the Pacific ENSO Applications Climate Center (PEAC), and partners provided reports on conditions across the Pacific Islands.
In the U.S. Affiliated Pacific Islands (USAPI) (maps — Federated States of Micronesia [FSM], Northern Mariana Islands, Marshall Islands [RMI], Republic of Palau [ROP], American Samoa, basinwide), May 2024 was drier than normal in the Republic of Palau and parts of the Marianas and FSM, but near to wetter than normal in American Samoa, the Marshalls, and other parts of the FSM and Marianas.
Monthly precipitation amounts were below the monthly minimum needed to meet most water needs (4 inches in the Marianas and Pago Pago, and 8 inches elsewhere) in the Marianas, Palau, northern Marshalls, and western FSM. May precipitation was above the monthly minimums in American Samoa and most of the FSM and Marshalls. The 4- and 8-inch thresholds are important because, if monthly precipitation falls below the threshold, then water shortages or drought become a concern.
The tropical Pacific climatology can experience extremes in precipitation, from very low precipitation during the dry season to very high precipitation during the wet season. This can result in monthly normal precipitation values that are different from the monthly minimum needed to meet most water needs, and this can lead to percent of normal values that seem odd. This was the case during May 2024, which is in the wet season for Palau, Kapingamarangi, Lukunor, Pohnpei, and Kosrae, and in the dry season for the Marianas, Marshalls, and Yap, with American Samoa entering the dry season. Precipitation was below the monthly minimum but above normal (1981-2010 normal), because the normals are low, at:
- Guam: May 2024 precipitation 3.82 inches, May normal mean 4.30 inches, April normal median 3.40 inches.
- Ulithi: May 2024 precipitation 6.34 inches, May normal mean 6.10 inches.
- Wotje: May 2024 precipitation 6.94 inches, May normal mean 4.92 inches.
Precipitation was above the monthly minimum but below normal (1981-2010 normal), because the normals are high, at:
- Chuuk: May 2024 precipitation 10.78 inches, May normal mean 11.73 inches, May normal median 11.30 inches.
- Kapingamarangi: May 2024 precipitation 11.42 inches, May normal mean 11.63 inches, May normal median 12.08 inches.
- Nukuoro: May 2024 precipitation 13.17 inches, May normal mean 14.61 inches.
- Jaluit: May 2024 precipitation 8.99 inches, May normal mean 10.85 inches.
In the table below, the station identified as Koror is Palau International Airport (Airai).
| Station Name | Jun 2023 | Jul 2023 | Aug 2023 | Sep 2023 | Oct 2023 | Nov 2023 | Dec 2023 | Jan 2024 | Feb 2024 | Mar 2024 | Apr 2024 | May 2024 | Jun- May |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chuuk | 118% | 130% | 118% | 112% | 110% | 141% | 100% | 100% | 76% | 40% | 99% | 95% | 101% |
| Guam NAS | 146% | 86% | 132% | 98% | 152% | 84% | 107% | 59% | 62% | 78% | 283% | 112% | 96% |
| Kapingamarangi | 145% | 162% | 121% | 256% | 117% | 153% | 74% | 188% | 206% | 196% | 99% | 95% | 132% |
| Koror | 77% | 145% | 125% | 130% | 108% | 85% | 67% | 136% | 140% | 48% | 184% | 59% | 99% |
| Kosrae | 166% | 132% | 104% | 123% | 153% | 163% | 44% | 90% | 119% | 96% | 84% | 124% | 96% |
| Kwajalein | 143% | 45% | 81% | 61% | 103% | 156% | 111% | 53% | 52% | 196% | 80% | 166% | 98% |
| Lukonor | 116% | 75% | 74% | 115% | 136% | 81% | 94% | 64% | 76% | 153% | 164% | 150% | 95% |
| Majuro | 105% | 70% | 95% | 56% | 86% | 101% | 70% | 57% | 74% | 16% | 111% | 150% | 84% |
| Pago Pago | 109% | 102% | 42% | 156% | 91% | 36% | 195% | 142% | 201% | 71% | 115% | 211% | 114% |
| Pohnpei | 121% | 148% | 219% | 156% | 83% | 178% | 48% | 50% | 170% | 91% | 116% | 121% | 120% |
| Saipan | 92% | 46% | 142% | 109% | 92% | 133% | 158% | 74% | 79% | 83% | 67% | 53% | 98% |
| Yap | 121% | 168% | 145% | 70% | 88% | 79% | 41% | 90% | 55% | 14% | 33% | 77% | 91% |
| Station Name | Jun 2023 | Jul 2023 | Aug 2023 | Sep 2023 | Oct 2023 | Nov 2023 | Dec 2023 | Jan 2024 | Feb 2024 | Mar 2024 | Apr 2024 | May 2024 | Jun- May |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chuuk | 13.73" | 15.56" | 15.23" | 13.07" | 12.70" | 14.93" | 11.22" | 10.05" | 5.49" | 3.30" | 12.38" | 10.78" | 138.44" |
| Guam NAS | 9.00" | 8.69" | 19.47" | 12.46" | 17.40" | 6.18" | 5.49" | 2.38" | 1.88" | 1.62" | 7.17" | 3.82" | 95.56" |
| Kapingamarangi | 20.04" | 22.86" | 9.87" | 25.45" | 9.55" | 14.14" | 7.33" | 17.18" | 19.05" | 22.43" | 13.53" | 11.42" | 192.85" |
| Koror | 13.44" | 26.81" | 16.86" | 15.26" | 12.80" | 9.65" | 7.46" | 13.85" | 11.97" | 3.56" | 13.44" | 7.01" | 152.11" |
| Kosrae | 24.30" | 19.67" | 14.72" | 17.52" | 16.79" | 22.60" | 7.06" | 15.04" | 15.43" | 15.34" | 14.64" | 21.96" | 205.07" |
| Kwajalein | 9.93" | 4.45" | 7.86" | 6.60" | 11.46" | 17.65" | 7.42" | 1.66" | 1.37" | 4.61" | 4.19" | 11.17" | 88.37" |
| Lukonor | 13.55" | 11.89" | 10.33" | 11.63" | 15.43" | 7.40" | 10.54" | 5.42" | 6.83" | 14.20" | 18.58" | 17.54" | 143.34" |
| Majuro | 11.56" | 7.87" | 11.07" | 6.27" | 10.98" | 13.51" | 7.96" | 4.38" | 5.11" | 1.08" | 10.43" | 15.17" | 105.39" |
| Pago Pago | 5.81" | 5.64" | 2.26" | 10.18" | 8.45" | 3.69" | 25.00" | 18.99" | 24.09" | 7.61" | 10.83" | 20.37" | 142.92" |
| Pohnpei | 17.94" | 22.76" | 31.21" | 19.57" | 12.71" | 26.39" | 7.76" | 6.65" | 16.27" | 12.02" | 21.36" | 24.07" | 218.71" |
| Saipan | 3.34" | 4.13" | 18.62" | 11.03" | 9.80" | 7.44" | 6.07" | 1.87" | 2.05" | 1.57" | 1.76" | 1.26" | 68.94" |
| Yap | 14.59" | 25.35" | 21.43" | 9.46" | 10.74" | 6.95" | 3.53" | 5.73" | 2.84" | 0.64" | 1.83" | 6.03" | 109.12" |
| Station Name | Jun 2023 | Jul 2023 | Aug 2023 | Sep 2023 | Oct 2023 | Nov 2023 | Dec 2023 | Jan 2024 | Feb 2024 | Mar 2024 | Apr 2024 | May 2024 | Jun- May |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chuuk | 11.66" | 11.98" | 12.86" | 11.71" | 11.51" | 10.61" | 11.25" | 10.10" | 7.25" | 8.32" | 12.47" | 11.30" | 136.77" |
| Guam NAS | 6.18" | 10.14" | 14.74" | 12.66" | 11.44" | 7.38" | 5.11" | 4.01" | 3.03" | 2.07" | 2.53" | 3.40" | 99.09" |
| Kapingamarangi | 13.78" | 14.15" | 8.13" | 9.93" | 8.19" | 9.27" | 9.84" | 9.15" | 9.27" | 11.43" | 13.64" | 12.08" | 145.85" |
| Koror | 17.48" | 18.53" | 13.50" | 11.77" | 11.84" | 11.39" | 11.16" | 10.18" | 8.56" | 7.44" | 7.32" | 11.83" | 152.90" |
| Kosrae | 14.64" | 14.91" | 14.22" | 14.22" | 10.94" | 13.83" | 16.11" | 16.67" | 12.93" | 16.06" | 17.51" | 17.75" | 213.87" |
| Kwajalein | 6.93" | 9.87" | 9.74" | 10.74" | 11.18" | 11.28" | 6.66" | 3.16" | 2.64" | 2.35" | 5.26" | 6.72" | 90.41" |
| Lukonor | 11.65" | 15.93" | 14.04" | 10.15" | 11.32" | 9.08" | 11.27" | 8.41" | 8.93" | 9.26" | 11.31" | 11.69" | 151.36" |
| Majuro | 11.01" | 11.17" | 11.69" | 11.17" | 12.73" | 13.44" | 11.39" | 7.74" | 6.88" | 6.58" | 9.42" | 10.11" | 125.25" |
| Pago Pago | 5.33" | 5.55" | 5.38" | 6.53" | 9.26" | 10.14" | 12.84" | 13.34" | 12.00" | 10.68" | 9.39" | 9.66" | 125.57" |
| Pohnpei | 14.81" | 15.43" | 14.26" | 12.55" | 15.27" | 14.83" | 16.08" | 13.18" | 9.55" | 13.17" | 18.41" | 19.96" | 182.36" |
| Saipan | 3.62" | 8.91" | 13.13" | 10.09" | 10.62" | 5.61" | 3.85" | 2.53" | 2.59" | 1.89" | 2.63" | 2.38" | 70.25" |
| Yap | 12.04" | 15.08" | 14.82" | 13.50" | 12.18" | 8.83" | 8.51" | 6.39" | 5.19" | 4.56" | 5.63" | 7.85" | 120.31" |
As measured by percent of normal precipitation, Yap was drier than normal at all time scales in the short term (May, the last 3 months [March-May], and the year-to-date [January-May]) and long term (last 12 months [June 2023-May 2024]). Airai, Chuuk, and Saipan were drier than normal in the short term and near to wetter than normal in the long term. Kosrae was wetter than normal in May but drier than normal for the other 3 time scales. Guam, Kwajalein, and Majuro were wetter than normal for the last 1 and 3 months but drier than normal at the 5- and 12-month time scales. Kapingamarangi was drier than normal in May but wetter than normal for the other 3 time scales. Lukunor was drier than normal at the 12-month time scale but wetter than normal for the other 3 time scales. Pago Pago and Pohnpei were near to wetter than normal in the short term and long term.
Based on percent of normal average (instead of normal median values), in the Marianas Islands, May and the last 2 to 12 months were drier than normal across the main islands, except Guam was wetter than normal at the 3-month time scale. A mixed precipitation anomaly pattern was evident at 60 months (percent of normal precipitation maps for the last 1, 3, 4, 12, 60 months).
Based on percent of normal average (instead of normal median values), the Marshall Islands were mostly wetter than normal in May, with drier-than-normal conditions dominating at the 3- to 12-month time scales; a mixed anomaly pattern was evident at 60 months (percent of normal precipitation maps for the last 1, 3, 4, 12, 60 months).
According to the May 31 USDM produced for the USAPI:
- In the Marianas, extreme drought continued on Saipan, severe drought continued on Guam, and moderate drought worsened to extreme drought on Rota;
- In the FSM, exceptional drought improved to extreme drought on Ulithi and Yap, severe drought improved to moderate drought then worsened back to severe drought at Woleai before improving again to moderate drought at the end of the month, and abnormal dryness ended at Chuuk;
- In the Marshalls, exceptional drought improved to moderate drought at Wotje, drought and abnormal dryness ended at Majuro, moderate drought improved to abnormal dryness at Kwajalein, and abnormal dryness ended at Ailinglaplap; and
- Abnormal dryness returned to Palau.
The level of the reservoir on Majuro began the month at 23.1 million gallons, steadily rose to a peak of 33.9 million gallons on the 27th, and ended the month at 33.2 million gallons. If the reservoir dips below 28.8 million gallons, drought becomes a concern. Satellite observations of vegetative health (drought stress, stressed vegetation, VHI) revealed areas of stressed vegetation on Guam.
The National Weather Service (NWS) office in Guam issued two Drought Information Statements (DGT) for drought for May (on May 10 and 24). Drought impacts included:
- water catchment levels were low or nearly empty on some islands. Water shortages for communities were occurring, especially for islands in northern Yap State (Yap Proper, Ulithi, Fais) and the northern RMI (Wotje and nearby islands). Rainfall later in May brought limited relief to these communities;
- agricultural strain was reported from islands across Yap State, where taro patches were drying up, coconuts were drying out, and there were many reports of yellowing crops;
- wildfires were reported on Guam, Saipan, Palau, and Yap;
- the Republic of Palau was on Stage 1 of the Drought Action Plan early in the month, but when water levels at major reservoirs returned to optimal levels, the country's National Emergency Committee rescinded the Stage 1 Drought Action Plan/Water Shortage Watch on May 14.
May 2024 precipitation ranks ranged from very dry to wet with some mid-range, based on data available at the time of this report. Some locations have had dry conditions for several months:
- Saipan: fourth driest May (in a 44-year record) and seventh driest January-May (year to date).
- Nukuoro: fourth driest February-May (41 years), but only 14th driest May.
- Ulithi: fourth driest March-May (40 years) and fifth driest November-May, but 21st driest (21st wettest) May.
- Kosrae: eighth driest December-May (45 years), but 39th driest (17th wettest) May.
- Woleai: eighth driest December-May (33 years), but 23rd driest (19th wettest) May.
- Yap: fourth driest December-May (73 years) and fifth driest March-May, February-May, January-May, November-May, and September-May; 19th driest June-May (12-month period); but only 21st driest May.
- Jaluit: fourth driest 12-month period June-May (38 years), but only 15th driest May.
- Majuro: ninth driest June-May and July-May (70 years), but 57th driest (14th wettest) May.
At the wet end of the scale:
- Pago Pago had the fourth wettest May (59 years) and wettest December-May (6-month period).
- Pohnpei had the 16th wettest May (73 years) and ninth wettest June-May (12-month period).
The following analysis of historical data for the USAPI stations in the Global Historical Climatology Network-Daily (GHCN-D) dataset, augmented with fill-in data from the 1981-2010 Normals, helps put the current data into historical perspective by computing ranks based on the period of record. The table below lists the precipitation ranks for May 2024, December 2023-May 2024 (last 6 months), and June 2023-May 2024 (the last 12 months). Some stations have a long period of record and their dataset is fairly complete, while other stations have a shorter period of record and the dataset has some missing data.
| Station | May 2024 | Dec 2023-May 2024 | Jun 2023-May 2024 | Period of Record | |||
|---|---|---|---|---|---|---|---|
| Rank | Years | Rank | Years | Rank | Years | ||
| Ailinglaplap | 36 | 41 | 22 | 39 | 24 | 38 | 1981-2024 |
| Airai | 6 | 73 | 22 | 73 | 35 | 71 | 1951-2024 |
| Chuuk | 22 | 73 | 16 | 73 | 29 | 72 | 1951-2024 |
| Fananu | -- | 8 | -- | 5 | -- | 4 | 2003-2023 |
| Guam | 36 | 68 | 24 | 67 | 28 | 67 | 1957-2024 |
| Jaluit | 15 | 41 | 7 | 39 | 4 | 38 | 1981-2024 |
| Kapingamarangi | 13 | 30 | 22 | 27 | 20 | 20 | 1962-2024 |
| Kosrae | 39 | 55 | 8 | 45 | 18 | 37 | 1954-2024 |
| Kwajalein | 51 | 73 | 27 | 72 | 17 | 72 | 1952-2024 |
| Lukunor | 31 | 40 | 29 | 39 | 16 | 27 | 1981-2024 |
| Majuro | 57 | 70 | 13 | 70 | 9 | 70 | 1954-2024 |
| Mili | -- | 39 | -- | 36 | -- | 34 | 1981-2024 |
| Nukuoro | 14 | 41 | 11 | 40 | 16 | 38 | 1981-2024 |
| Pago Pago | 56 | 59 | 58 | 58 | 47 | 58 | 1966-2024 |
| Pingelap | -- | 39 | -- | 35 | -- | 34 | 1981-2024 |
| Pohnpei | 58 | 73 | 31 | 73 | 64 | 72 | 1951-2024 |
| Saipan | 4 | 44 | 11 | 35 | 16 | 35 | 1981-2024 |
| Ulithi | 21 | 41 | 7 | 38 | 21 | 36 | 1981-2024 |
| Utirik | -- | 20 | -- | 9 | -- | 4 | 1985-2020 |
| Woleai | 23 | 41 | 8 | 33 | 12 | 26 | 1968-2024 |
| Wotje | 33 | 40 | 25 | 37 | 12 | 36 | 1981-2024 |
| Yap | 21 | 73 | 4 | 73 | 19 | 72 | 1951-2024 |
SPI values for seven time periods for Pacific Islands, computed by the Honolulu NWS office.
NOAA Regional Climate Centers
More information, provided by the NOAA Regional Climate Centers and others, can be found below.
Southeast
As noted by the Southeast Regional Climate Center, temperatures were above average across most of the Southeast in May, and precipitation was above average across much of the region, following a relatively dry April. The heat and dryness across Florida were especially noteworthy. Precipitation was below average across much of the Florida Peninsula, as well as central portions of Alabama, Georgia, South Carolina, and Virginia. The driest locations were found across parts of central and southern Florida, where monthly totals were over 4 inches (102 mm) below average in places (less than 25 percent of normal). Several locations, including Tampa, West Palm Beach, and Fort Lauderdale, recorded around 1 inch (25 mm) of precipitation, while Naples and Sarasota recorded less than an inch.
Temperatures and precipitation were above average across Puerto Rico and the U.S. Virgin Islands. San Juan, PR recorded its warmest May on record (since 1898). On the 12th and 21st, San Juan reached 95 degrees F (35 degrees C), which is just 1 degree F (0.5 degrees C) shy of its highest monthly maximum temperature on record. Extreme heat was also recorded on Saint Croix, with the heat index reaching 116 degrees F (46.7 degrees C) on the 5th and 115 degrees F (46.1 degrees C) on the 26th.
Drought conditions improved across the northern half of the region and in the Caribbean but worsened across much of South Florida. By the end of the month, only small pockets of abnormal dryness (D0) were found scattered across parts of Alabama, the Carolinas, and Virginia, while Puerto Rico and the U.S. Virgin Islands were free of any drought or abnormal dryness. On the other hand, moderate (D1) drought expanded across much of the southern half of the Florida Peninsula, with a band of severe (D2) drought emerging across the Citrus Belt from just north of Fort Myers to Lake Okeechobee. The heat and lack of rain across the Citrus Belt of Florida required extra irrigation as ponds were drying up. Pastures and cattle also showed signs of heat and drought stress.
South
As explained by the Southern Regional Climate Center, flooding, tornadoes, hail, and winds severely impacted large swaths of the Southern region during May. Temperatures were above normal for the entirety of the Southern region during the month, with the greatest departures being recorded in South Texas where most stations were four to eight degrees F above normal. Precipitation was well above normal for the majority of the Southern region during May, with below-normal precipitation largely confined to Deep South and West Texas where stations ranged from five to 70 percent of normal for the month.
During May, 69 percent of the Southern region remained drought free as of May 28th according to the USDM. Areas experiencing drought include Deep South Texas, Central Texas, West Texas, the Texas and Oklahoma Panhandles, northern Oklahoma, and northeastern Arkansas. One class degradation in drought conditions was common in the Texas and Oklahoma Panhandles, and Deep South Texas. One to three class improvements were noted across northern Oklahoma, Central Texas, northern Arkansas, northwestern Mississippi, eastern Tennessee, and western Tennessee. With ample spring precipitation and suitable temperatures in winter wheat production areas (Texas, Oklahoma, and Arkansas), the condition of winter wheat crops improved over this time last year, though Texas is lagging behind the other wheat producers in terms of crop condition. As of May 26th, the USDA reported the percentage of winter wheat crops as being in good to excellent condition at the state level: Arkansas (65 precent), Oklahoma (53 percent), and Texas (36 percent).
Midwest
As described by the Midwest Regional Climate Center, the preliminary average May temperature for the Midwest was 62.5 degrees F (16.9 degrees C), which was 2.8 degrees F (1.6 degrees C) above the 1991-2020 normal, and preliminary May precipitation totaled 5.71 inches (145 mm) for the Midwest, which was 1.33 inches (34 mm) above normal, or 130 percent of normal. Preliminary rankings indicate that spring 2024 was the 2nd wettest in the 1895-2024 record but tied for the 4th warmest. The ample precipitation across the region supported continued drought improvement throughout May. Less than 1 percent of the region was in drought by month's end, and just 7 percent had abnormally dry conditions. After 203 consecutive weeks, the removal of drought conditions in Iowa in late May marked the first time since June 2020 that the state was completely drought-free.
Northeast
As summarized by the Northeast Regional Climate Center, while May featured warm temperatures and variable precipitation, the spring season was decidedly warm and wet. During May, the Northeast received 3.62 inches of precipitation, which was 91 percent of normal, and May temperatures ranked 10th warmest in 130 years of recordkeeping, with an average temperature of 60.3 degrees F, 3.4 degrees F above normal. Spring 2024 was the fourth-warmest and 13th wettest spring since 1895 for the Northeast.
The USDM from May 7 showed abnormal dryness covered three percent of the Northeast, including northwestern Maine and parts of western and central New York. Due to factors such as reduced soil moisture, below-normal groundwater levels, and continued precipitation deficits, abnormal dryness persisted in western/central New York, expanded slightly in northwestern Maine, and was introduced on the Delmarva Peninsula and in a small section of eastern West Virginia. The USDM from May 28 showed four percent of the Northeast as abnormally dry.
High Plains
As discussed by the High Plains Regional Climate Center, May featured a steady stream of severe weather, with temperatures split across the region and precipitation scattered but also abundant. The areas that did receive rainfall were often over 150 percent of their normal, with some localized amounts exceeding 10 inches this month. Among those who missed out this month were the areas in and around Cheyenne, Wyoming. The city only measured 0.34 inch (8.64 mm) of precipitation to rank May as 7th driest. Nearby Laramie fared slightly better with 0.57 inch (14.48 mm) but also ranked 7th driest.
The continual rounds of heavy precipitation have greatly improved drought conditions across the High Plains in recent months. Some parts of the western Plains experienced degradation this month, but the region saw a reduction of over 9 percent in D0 to D4 (abnormally dry to exceptional drought conditions). The drought that had gripped Nebraska since 2021 is nearly erased. D2 (severe drought) has been eliminated from the state for the first time since June 1st, 2021. This is also a drastic shift from last year when close to 11 percent of the state was engulfed by D4. Conditions are likely to continue to improve in the state, with standing water common across the eastern part of the state. Near-record precipitation in North Dakota led to significant improvements, with D0-D4 reduced by 29 percent this month. Only a small sliver of drought conditions remains in the western border, with over 80 percent of the state drought-free. The lone source of concern, once again, in the region is western Kansas. Two small patches of D3 (extreme drought) were reintroduced, but it could be short-lived due to recent rains. Elsewhere in the region, other improvements and degradation were observed.
West
As summarized by the Western Regional Climate Center, conditions were generally cooler and drier than normal across the West during May. Strong low pressure and storminess persisted for much of the month over the northern tier of the West bringing with it well-below normal temperatures for much of the northern Great Basin and northern Rockies. Extremely dry conditions, not uncommon for this time of year, prevailed throughout the Southwest with little drought relief for Arizona and New Mexico.
Below-normal precipitation occurred in parts of all western states with large areas of zero to 25 percent of normal in Nevada, Arizona, southern California, southern New Mexico, and much of Utah. Zero precipitation was observed for many locations in the desert Southwest which is not all that uncommon for May. Cavern City airport, in southeast New Mexico, received just 0.01 inch of precipitation for the month which is tied for the fifth driest on record and is 1.14 inches below normal. The hot and dry conditions in southern New Mexico have worsened drought and this area is the only part of the West with exceptional drought (D4) present.
According to the USDM at the end of May, 19 percent of the West was in drought. No areas of drought are found in California, Nevada, and Oregon. Areas of extreme (D3) and exceptional (D4) drought are found in southern New Mexico and a small pocket of D3 is found near the northern Idaho-northwest Montana border. Drought expanded in parts of Washington and improvements were made in parts of Oregon and Montana.
Alaska: May temperatures were one to four degrees Fahrenheit below normal for much of Alaska with isolated locations seeing departures up to nine degrees Fahrenheit below normal. Wetter-than-normal conditions occurred in much of the southern half of the state, including the Panhandle, with drier-than-normal conditions in northwest Alaska and the southern extent of the Aleutian Islands.
Hawaii: Most of Hawaii saw above-normal precipitation for May except for the northeast coast of the Big Island and parts of Molokai and Lanai. A slow-moving Kona Low set up to the northwest of Hawaii and brought heavy rainfall, flooding, and rockslides May 14-17. Oahu was not in drought at the beginning of May; however, much of the Big Island was in moderate (D1) or severe (D2) drought at the beginning of May and heavy rainfall during the month substantially reduced the spatial extent of drought on the island. At the end of May, just 8.24 percent of Hawaii was in drought according to the USDM.