NOAA's National Centers for Environmental Information
Issued 14 January 2022
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 20% of the contiguous United States as of the end of December 2021, a decrease of about 9% from last month. About 3% of the contiguous U.S. fell in the severely to extremely wet categories.
- About 41% of the contiguous U.S. fell in the moderate to extreme drought categories (based on the Palmer Drought Index) at the end of December.
- 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".
U.S. Drought Monitor information is currently unavailable.
Detailed Drought Overview
The upper-level circulation during December 2021 was very active with several shortwave troughs and closed lows moving through the jet stream flow. But they moved through a long-wave pattern that shifted position early in the month, eventually settling during the last half of the month into a long-wave trough in the West and ridge over the eastern CONUS. The shortwave troughs brought Pacific fronts with them that blanketed much of the West with above-normal precipitation and an improved mountain snowpack. With the predominance of ridging east of the Rockies, precipitation was below normal across the southern to central Plains and across the Gulf of Mexico and Atlantic coasts. Only the northern Plains to western Great Lakes and Ohio Valley states had a wetter-than-normal month. Monthly temperatures were also above normal for most of the CONUS with excessively abnormal temperatures for this time of year across the southern Plains to Ohio Valley. The unusually warm to record warm temperatures increased evapotranspiration which exacerbated drought conditions for those areas that have been dry, especially for the southern Plains to Lower Mississippi Valley states but also for the Mid-Atlantic states. The hot temperatures and lack of precipitation in the southern Plains were accompanied by low relative humidity, all of which conspired to sap the soils of moisture even more.
As a result of these conditions, drought or abnormal dryness expanded or intensified in the southern to central Plains, Lower Mississippi Valley, and Southeast to Mid-Atlantic Coast. (Above-normal precipitation at the very end of December and early January improved conditions in the Southeast to Mid-Atlantic from the December 28 USDM map to the January 4 USDM map, but conditions deteriorated in the region from the November 30 USDM map to December 28 USDM map.) Beneficial precipitation caused drought or abnormal dryness to contract or decrease in intensity across much of the West and parts of the northern Plains, and heavy rains from a Kona Low and subsequent showers improved conditions across Hawaii. Drought expansion exceeded contraction with the USDM-based national moderate-to-exceptional drought footprint across the CONUS rising from 53.4 percent at the end of November to 54.8 percent at the end of December (from 44.8 percent to 45.8 percent for the 50 States and Puerto Rico). According to the Palmer Drought Index, which goes back to the beginning of the 20th century, about 41.2 percent of the CONUS was in moderate to extreme drought at the end of December, which is about the same as the end of November. The percent area of the CONUS in moderate to extreme drought has hovered between 35 and 49 percent for the last 16 months (since September 2020).
Drought conditions at the end of December, as depicted on the January 4, 2022 USDM map, included the following core drought and abnormally dry areas:
- Moderate (D1) to severe (D2) drought extended from the West Coast to Rocky Mountains and into the adjacent Great Plains, with a large areas of extreme (D3) to exceptional (D4) drought. Long-term drought indicators such as reservoir levels improved but some continued to be low. Mountain snowpack and streamflow indicators improved, although some were still low. Soil moisture was still low in some areas. The percent area of the West experiencing moderate to exceptional drought, according to USDM statistics, decreased slightly from 94.0 percent at the end of November to 89.3 percent at the end of December. The percent area of the West (from the Rockies to the West Coast) in moderate to extreme drought (based on the Palmer Drought Index) shrank to 59.5 percent at the end of December 2021.
- Drought contracted or reduced in intensity in parts of the northern Plains but expanded or intensified in parts of the central Plains and across most of the southern Plains to Lower Mississippi Valley. For the central to northern Plains taken together, the moderate to extreme drought area expanded slightly from 63.9 percent at the end of November to 64.8 percent at the end of December. In the southern Plains, moderate to extreme drought ballooned from 54.2 percent at the end of November to 81.7 percent at the end of December. Taken together, the southern Plains and Lower Mississippi Valley (South Region) saw moderate to extreme drought jump from 41.7 percent at the end of November to 62.4 percent at the end of November. The explosive growth of drought this month in the South was fueled by continued lack of precipitation and record high temperatures, and was reflected in dry soils, high evapotranspiration, low groundwater, low reservoirs (in western Texas), stressed vegetation, and a rash of wildfires during the last half of the month (wildfire maps for December 2, 7, 11, 17, 20, 21, 24, 28, 31).
- Drought or abnormal dryness expanded in some parts of the Midwest and contracted in other parts. Extreme drought disappeared from the region this month. Overall, the drought area contracted from 17.3 percent at the end of November to 15.3 percent at the end of December. The worst drought areas continued in the western Great Lakes and Upper Mississippi Valley.
- Moderate to severe drought continued in the Northeast, hovering at about 2.0 percent of the region. Some expansion of abnormal dryness occurred in southern portions, with a few spots of moderate drought briefly appearing on the December 28 USDM map. What little drought remained was in northern Maine and New Hampshire.
- In the Southeast, moderate and severe drought expanded in the Carolinas and adjacent Virginia to reach 28.0 percent of the region on December 28. Precipitation on subsequent days shrank the drought area, with the net effect being a slight contraction of the drought area from 17.7 percent at the end of November to 16.2 percent at the end of December (January 4, 2022). The dry conditions were reflected in high evapotranspiration, low soil moisture, low streamflow, and an outbreak of wildfires early in the month.
- In Hawaii, heavy rains from a Kona Low and subsequent showers eliminated drought from the state, with just a few areas of abnormal dryness remaining on a couple islands on the January 4 USDM map.
- In the Caribbean, moderate drought contracted slightly on Puerto Rico, with the drought area changing from 29.0 percent at the end of November to 28.0 percent at the end of December. Drought intensified in the U.S. Virgin Islands (USVI), with extreme drought developing in the south on St. Croix, severe drought developing on St. Thomas, and moderate drought developing on St. John.
- In the U.S.-Affiliated Pacific Islands (USAPI), compared to last month, extreme drought at Kapingamarangi (Federated States of Micronesia) improved to moderate drought, moderate drought developed at Wotje and abnormal dryness developed at Kwajalein (Marshall Islands), and abnormal dryness developed at Guam.
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 across the southern to central Plains and Mid-Atlantic regions, expanding or intensifying drought. Short-term drought occurred across the Lower Mississippi Valley and Gulf Coast, and in southern New England, reducing long-term wet conditions in these regions (PHDI maps for December compared to November). Short-term wet conditions in the northern Plains and Upper Mississippi Valley, and across much of the West, contracted or decreased the intensity of long-term drought in these regions.
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 covered much of the southern to central Plains and Gulf of Mexico coast at the 1- to 2-month time scales; much of the southern Plains and Lower Mississippi Valley and parts of the central Plains at 3 months; much of the southern and central High Plains (western portions of the Plains) at 6 and 24 months; and much of the central Plains at 9 months. Much of the southern Appalachians and Mid-Atlantic to southern New England region was dry at 1 to 2 months, with the dryness extensive across the southern Appalachians to Mid-Atlantic at the 3-month time scale, and parts of the southern Appalachians to Carolina coast dry at 6 to 12 months. Northern New England has some dryness at 3 and 9 to 24 months, while southern Florida is dry at 12 months. Parts of Montana are dry at 6 months, with the dry area extending to the Pacific Northwest and across the northern Plains to Upper Mississippi Valley at 9 to 24 months. Much of the West is wet at 1 to 6 months, but dryness becomes evident in the Pacific Northwest starting at 9 months and in the Southwest starting at 12 months, with very dry conditions widespread across the West at 24 months. Wet conditions dominate the northern Plains to Upper Mississippi Valley at 1 to 3 months, extend from the southern Great Lakes to Northeast at 3 to 24 months, stretch from the Great Lakes to Gulf of Mexico coast at 6 to 24 months, and cover much of the Lower and Mid-Mississippi and Ohio Valleys to Atlantic and Gulf coasts at 24 months. An interesting pattern continues at the 24-month time scale — very dry conditions dominate across the West to northern Plains, while very wet conditions dominate the Deep South to Atlantic Coast.
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, December marks the beginning of climatological winter, which is the coldest season when evapotranspiration is minimal. During December 2021, however, temperatures were well above normal across most of the CONUS east of the Rockies as well as much of the Southwest, with record warm temperatures across the southern to central Plains and Lower Mississippi Valley. These records were exceptional, exceeding the previous records by several degrees in states such as Arkansas, Louisiana, Oklahoma, and Texas.
Such exceedingly warm temperatures enhanced evapotranspiration in these southerly latitudes, even at this time of year. When combined with low precipitation, the warm temperatures resulted in SPEI values that far exceeded the corresponding SPI values. This was the case for the last several months in the southern Plains, Lower Mississippi Valley, and Mid-Atlantic states (SPEI maps for last 1, 2, 3, 6 months) (SPI maps for last 1, 2, 3, 6 months). States with record dry SPEI values, and corresponding SPI values (that were not record dry in most cases), include:
- Delaware (SPEI for last 1 and 2 months) (SPI for last 1 and 2 months)
- Kansas (SPEI for last 1 and 2 months) (SPI for last 1 and 2 months)
- Lousiana (SPEI for last 1, 2, and 3 months) (SPI for last 1, 2, and 3 months)
- Mississippi (SPEI for last 2 months) (SPI for last 2 months)
- New Jersey (SPEI for last 2 months) (SPI for last 2 months)
- Oklahoma (SPEI for last 1 month) (SPI for last 1 month)
- Texas (SPEI for last 1 and 2 months) (SPI for last 1 and 2 months)
Unusual warmth in the West earlier in the year, especially in the Pacific Northwest and California-Nevada, resulted in SPEI values that were more extreme than the corresponding SPI values (SPEI maps for last 9 and 12 months) (SPI maps for last 9 and 12 months).
The western U.S. has been excessively warm in previous years as well as in 2021. This persistent heat has resulted in SPEI values that were drier than the corresponding SPI values for the last several years (SPEI maps for last 18, 24, 36, 48, 60, and 72 months) (SPI maps for last 18, 24, 36, 48, 60, and 72 months). The precipitation that has occurred in the West during the last half of 2021 has helped reduce the severity of the drought. However, the dryness and heat over the last several years has been so severe that Arizona still has the most extreme SPEI on record for the last 5 and 6 years, in spite of the recent precipitation.
Regional Discussion
Hawaii
A Kona Low gave Hawaii above-normal precipitation during December 2021. The wet conditions during December were so great that they neutralized dryness back several months so that near to above-normal conditions dominated most of the state for the last 1 to 4 months. Dry conditions were evident at a few stations at the 6- to 9-month time scales, with wetter-than-normal conditions dominating at 12 months. Areas of drier-than-normal precipitation could be found on Oahu to the Big Island at 24 to 36 months, but wetter-than-normal anomalies dominated at longer time periods (last 1, 2, 3, 4, 6, 9, 12, 24, 36, 48, 60 months) (climate engine model percent of normal precipitation map for the last month). Monthly streamflow was near to above normal across most of the state. Drought ended this month, with the overall drought footprint falling from 56.8 percent of the state at the end of November to zero percent on the January 4th USDM map. Only a few areas of abnormal dryness remained.
Alaska
December 2021 was drier than normal across southern coastal Alaska, the Aleutian Chain, and the panhandle, and wetter than normal across most of the rest of the state. This pattern was evident for the last 2 to 12 months, with drier-than-normal conditions extending further into the Cook Inlet and Bristol Bay climate divisions and occurring at a few stations in the North Slope division, while the panhandle was less dry. This general pattern was evident at longer time scales, except some stations were wetter-than-normal scattered in the dry regions (low elevation station precipitation anomaly maps for the last 1, 2, 3, 4, 6, 9, 12, 24, 36, 48, 60 months) (high elevation SNOTEL station precipitation anomaly maps for the last 1 and 3 months) (SNOTEL basin precipitation anomaly map for the last 3 months) (climate division precipitation rank maps for the last 1, 3, 6, and 12 months) (climate engine model percent of normal precipitation map for the last month) (modeled percent of normal maps from ACCAP for the last 3 months) (Leaky Bucket model precipitation percentile map).
December was colder than normal across most of the state, with some warmer-than-normal stations in the west, southwest, and central to southeast interior areas. Near to cooler-than-normal conditions dominated for the last 2-12 months (low elevation station temperature anomaly maps for the last 1, 2, 3, 4, 12 months) (climate division temperature rank maps for the last 1, 3, 6, and 12 months) (Leaky Bucket model temperature percentile map). End-of-December satellite-based and SNOTEL (station, basin) observations of snow water equivalent (SWE) in snowpack were mostly near to above average with some below-average areas (especially in the south central coastal areas).
Monthly streamflow (for those streams that were not frozen) showed a mixed anomaly pattern with some below-normal streamflows in the south central coastal and panhandle regions. There was no drought or abnormal dryness on the January 4th USDM map.
Puerto Rico and U.S. Virgin Islands
December 2021 was much drier than normal across the U.S. Virgin Islands (USVI) and parts of Puerto Rico (PR), with some locations in PR having a wetter-than-normal month. Drier-than-normal conditions dominated the USVI and PR for the last 2 to 6 months and most of PR at 9 to 48 months. PR had a mixed anomaly pattern at the 60-month time scale (radar-based precipitation anomaly estimates for the last 1, 2, 3, 6, 12 months) (low elevation station precipitation maps for the last 1, 2, 3, 4, 6, 9, 12, 24, 36, 48, 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 warmer than normal for much of the USVI and PR during December with a mixed temperature anomaly pattern for October-December. Root zone analyses indicated that soil conditions were dry along the southern and northern coasts and eastern interior regions of PR with some dryness developing in interior regions (root zone soil saturation fraction; relative soil moisture at 0-10 cm [0-4 in], 10-40 cm [4-16 in], 40-100 cm [16-39 in], 100-200 cm [39-79 in] depth). Monthly streamflow in PR had below normal gauges interspersed with near normal gauges. In the USVI, groundwater continued to decline throughout December on St. Croix and St. John, and fluctuated up and down on St. Thomas. On St. Croix, end-of-December 2021 levels had exceeded the record low levels that occurred in 2016. On St. Thomas and St. John, groundwater levels were low but not at the record low values that occurred in 2016-17. Moderate drought shrank slightly from 29.0 percent of Puerto Rico at the end of November to 28.0 percent at the end of December. Conditions deteriorated in the USVI, with extreme drought developing in the south on St. Croix, severe drought developing on St. Thomas, and moderate drought developing on St. John.
CONUS State Precipitation Ranks
December 2021 was drier than normal across the southern to central Plains, Gulf of Mexico coast, and southern Appalachians to southern New England. Eighteen states had a precipitation rank in the driest third of the 127-year historical record for December, including seven in the top ten driest category — Delaware (fifth driest); New Jersey (sixth driest); Louisiana, Maryland, and Virginia (each seventh driest); and Kansas and Texas (both tenth driest).
October-December 2021 was drier than normal across the southern to central Plains, Lower Mississippi Valley to southern Appalachians, and Mid-Atlantic states to much of New England, as well as parts of the Southwest, western Great Lakes, and Montana. Record dryness occurred locally in eastern Colorado. Fourteen states had a precipitation rank in the driest third of the 1895-2021 historical record for October-December, including five in the top ten driest category — Delaware (fourth driest); Louisiana (sixth driest); Virginia (ninth driest); and Maryland and North Carolina (both tenth driest). Colorado, which had record dryness in the Plains in the eastern part of the state, had above-normal precipitation over the Rockies in the west, which gave the state a rank of 48th driest.
July-December 2021 was drier than normal across the southern to central Plains, Lower Mississippi Valley, Carolinas to West Virginia, and parts of the western Great Lakes and Montana. Eight states had a precipitation rank in the driest third of the 1895-2021 historical record, but none ranked in the top ten driest category.
January-December 2021 was drier than normal across much of the West, Great Plains, and Upper Mississippi Valley, and parts of the southern Appalachian, Mid-Atlantic, and northern New England states and southern Florida. Record dryness occurred locally in Montana. Twelve states had a precipitation rank in the driest third of the 1895-2021 historical record, including one in the top ten driest category — Montana ranked ninth driest.
Agricultural Belts
During December 2021, the Primary Hard Red Winter Wheat agricultural belt was warmer and drier than average. The month ranked as the warmest and fourth driest December, regionwide, in the 1895-2021 record.
October marks the beginning of the growing season for the Primary Hard Red Winter Wheat belt. October-December 2021 was also warmer and drier than normal. The period ranked as the warmest and 35th driest October-December, regionwide, on record.
As of January 4, 2022, drought affected approximately 76 percent of barley production, 69 percent of sorghum production, 65 percent of winter wheat production, 65 percent of the sheep inventory, 55 percent of cotton production, 53 percent of spring wheat production, 50 percent of the cattle inventory, 47 percent of the milk cow inventory, 44 percent of hay acreage, 30 percent of rice production, 18 percent of corn production, and 14 percent of soybean production.
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, American Samoa, basinwide), December 2021 was drier-than-normal in the RMI, Guam, American Samoa, and parts of the FSM. It was near to wetter than normal across Palau, most of the FSM, and the Marianas north of Guam.
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) at Kwajalein and Wotje (in the RMI) and Nukuro (in the FSM). December precipitation was above the monthly minimums at the rest of the stations across the USAPI. The 4- and 8-inch thresholds are important because, if monthly precipitation falls below the threshold, then water shortages or drought become a concern.
In the table below, the station identified as Koror is Palau International Airport (Airai).
| Station Name | Jan 2021 | Feb 2021 | Mar 2021 | Apr 2021 | May 2021 | Jun 2021 | Jul 2021 | Aug 2021 | Sep 2021 | Oct 2021 | Nov 2021 | Dec 2021 | Jan- Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chuuk | 114% | 156% | 223% | 55% | 244% | 60% | 135% | 48% | 143% | 138% | 112% | 149% | 122% |
| Guam NAS | 102% | 33% | 130% | 119% | 210% | 82% | 86% | 105% | 92% | 233% | 134% | 87% | 101% |
| Kapingamarangi | 65% | 63% | 78% | 150% | 129% | 72% | 99% | 52% | 40% | 30% | 29% | 148% | 74% |
| Koror | 102% | 166% | 119% | 287% | 178% | 56% | 73% | 101% | 164% | 233% | 70% | 155% | 121% |
| Kosrae | 188% | 141% | 194% | 106% | 154% | 194% | 166% | 67% | 107% | 129% | 122% | 160% | 122% |
| Kwajalein | 74% | 75% | 264% | 174% | 126% | 67% | 82% | 35% | 105% | 98% | 128% | 56% | 94% |
| Lukonor | 146% | 180% | 84% | 134% | 238% | 105% | 41% | 63% | 94% | 64% | 145% | 152% | 102% |
| Majuro | 150% | 57% | 228% | 135% | 285% | 84% | 84% | 91% | 111% | 119% | 130% | 77% | 124% |
| Pago Pago | 132% | 141% | 91% | 76% | 80% | 212% | 84% | 145% | 51% | 47% | 124% | 61% | 88% |
| Pohnpei | 147% | 65% | 216% | 77% | 152% | 141% | 93% | 66% | 105% | 95% | 174% | 96% | 116% |
| Saipan | 91% | 122% | 46% | 77% | 120% | 158% | 123% | 83% | 85% | 100% | 138% | 141% | 101% |
| Yap | 201% | 139% | 189% | 316% | 109% | 86% | 67% | 87% | 93% | 107% | 64% | 145% | 110% |
| Station Name | Jan 2021 | Feb 2021 | Mar 2021 | Apr 2021 | May 2021 | Jun 2021 | Jul 2021 | Aug 2021 | Sep 2021 | Oct 2021 | Nov 2021 | Dec 2021 | Jan- Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chuuk | 11.56" | 11.29" | 18.55" | 6.86" | 27.53" | 7.00" | 16.13" | 6.20" | 16.70" | 15.86" | 11.89" | 16.79" | 166.36" |
| Guam NAS | 4.11" | 1.01" | 2.70" | 3.02" | 7.14" | 5.08" | 8.76" | 15.44" | 11.61" | 26.68" | 9.87" | 4.47" | 99.89" |
| Kapingamarangi | 5.92" | 5.86" | 8.91" | 20.44" | 15.53" | 9.95" | 14.01" | 4.26" | 3.98" | 2.46" | 2.66" | 14.57" | 108.55" |
| Koror | 10.42" | 14.23" | 8.84" | 21.03" | 21.06" | 9.87" | 13.55" | 13.66" | 19.33" | 27.58" | 7.95" | 17.35" | 184.87" |
| Kosrae | 31.36" | 18.28" | 31.20" | 18.63" | 27.37" | 28.33" | 24.77" | 9.48" | 15.27" | 14.15" | 16.81" | 25.70" | 261.35" |
| Kwajalein | 2.34" | 1.97" | 6.21" | 9.17" | 8.45" | 4.61" | 8.05" | 3.43" | 11.30" | 10.97" | 14.47" | 3.74" | 84.71" |
| Lukonor | 12.29" | 16.11" | 7.81" | 15.21" | 27.86" | 12.26" | 6.61" | 8.83" | 9.50" | 7.25" | 13.20" | 17.10" | 154.03" |
| Majuro | 11.58" | 3.89" | 15.00" | 12.71" | 28.81" | 9.28" | 9.42" | 10.60" | 12.41" | 15.12" | 17.42" | 8.76" | 155" |
| Pago Pago | 17.62" | 16.86" | 9.68" | 7.14" | 7.71" | 11.32" | 4.64" | 7.82" | 3.33" | 4.38" | 12.58" | 7.83" | 110.91" |
| Pohnpei | 19.38" | 6.24" | 28.50" | 14.18" | 30.38" | 20.95" | 14.30" | 9.35" | 13.18" | 14.57" | 25.82" | 15.49" | 212.34" |
| Saipan | 2.30" | 3.15" | 0.86" | 2.02" | 2.85" | 5.71" | 10.94" | 10.95" | 8.62" | 10.63" | 7.76" | 5.41" | 71.2" |
| Yap | 12.85" | 7.24" | 8.63" | 17.78" | 8.59" | 10.35" | 10.13" | 12.84" | 12.55" | 13.00" | 5.68" | 12.31" | 131.95" |
| Station Name | Jan 2021 | Feb 2021 | Mar 2021 | Apr 2021 | May 2021 | Jun 2021 | Jul 2021 | Aug 2021 | Sep 2021 | Oct 2021 | Nov 2021 | Dec 2021 | Jan- Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chuuk | 10.10" | 7.25" | 8.32" | 12.47" | 11.30" | 11.66" | 11.98" | 12.86" | 11.71" | 11.51" | 10.61" | 11.25" | 136.77" |
| Guam NAS | 4.01" | 3.03" | 2.07" | 2.53" | 3.40" | 6.18" | 10.14" | 14.74" | 12.66" | 11.44" | 7.38" | 5.11" | 99.09" |
| Kapingamarangi | 9.15" | 9.27" | 11.43" | 13.64" | 12.08" | 13.78" | 14.15" | 8.13" | 9.93" | 8.19" | 9.27" | 9.84" | 145.85" |
| Koror | 10.18" | 8.56" | 7.44" | 7.32" | 11.83" | 17.48" | 18.53" | 13.50" | 11.77" | 11.84" | 11.39" | 11.16" | 152.90" |
| Kosrae | 16.67" | 12.93" | 16.06" | 17.51" | 17.75" | 14.64" | 14.91" | 14.22" | 14.22" | 10.94" | 13.83" | 16.11" | 213.87" |
| Kwajalein | 3.16" | 2.64" | 2.35" | 5.26" | 6.72" | 6.93" | 9.87" | 9.74" | 10.74" | 11.18" | 11.28" | 6.66" | 90.41" |
| Lukonor | 8.41" | 8.93" | 9.26" | 11.31" | 11.69" | 11.65" | 15.93" | 14.04" | 10.15" | 11.32" | 9.08" | 11.27" | 151.36" |
| Majuro | 7.74" | 6.88" | 6.58" | 9.42" | 10.11" | 11.01" | 11.17" | 11.69" | 11.17" | 12.73" | 13.44" | 11.39" | 125.25" |
| Pago Pago | 13.34" | 12.00" | 10.68" | 9.39" | 9.66" | 5.33" | 5.55" | 5.38" | 6.53" | 9.26" | 10.14" | 12.84" | 125.57" |
| Pohnpei | 13.18" | 9.55" | 13.17" | 18.41" | 19.96" | 14.81" | 15.43" | 14.26" | 12.55" | 15.27" | 14.83" | 16.08" | 182.36" |
| Saipan | 2.53" | 2.59" | 1.89" | 2.63" | 2.38" | 3.62" | 8.91" | 13.13" | 10.09" | 10.62" | 5.61" | 3.85" | 70.25" |
| Yap | 6.39" | 5.19" | 4.56" | 5.63" | 7.85" | 12.04" | 15.08" | 14.82" | 13.50" | 12.18" | 8.83" | 8.51" | 120.31" |
As measured by percent of normal precipitation, Kwajalein and Pago Pago were drier than normal in the short term (December and the last 3 months [October-December 2021]) and long term (last 12 months [January-December 2021]). Kapingamarangi was drier than normal at the 3- and 12-month time scales and wetter than normal for December. Guam, Majuro, and Pohnpei were drier than normal for December but near to wetter than normal at the other two time scales. Airai, Chuuk, Kosrae, Lukunor, Saipan, and Yap were near to wetter than normal at all three time scales.
Based on percent of normal average (instead of normal median values), in the Marianas Islands, precipitation during December was mostly above normal across the islands except drier than normal on Guam. By three months the anomaly pattern shifts to drier than normal at Rota and wetter than normal elsewhere. Drier-than-normal conditions dominate across most stations by 6 months with wetter-than-normal conditions on Guam and drier than normal north by 12 months. At longer time scales, precipitation was above normal at the southern extreme of Guam and northern extreme of Saipan, with below normal anomalies in between (percent of normal precipitation maps for the last 1, 2, 3, 4, 6, 9, 12, 24, 36, 48, 60 months).
Based on percent of normal average (instead of normal median values), in the Marshall Islands, precipitation during December was generally below normal in the east and north and above normal in the southwest. By 3 months the northern islands were drier than normal while the rest of the RMI was near to wetter than normal. Drier-than-normal conditions dominated at most stations at 6 to 9 months, with a mixed pattern at longer time scales (percent of normal precipitation maps for the last 1, 2, 3, 4, 6, 9, 12, 24, 36, 48, 60 months).
![0-10 cm [0-4 in]](/monitoring-content/sotc/drought/2021/12/rsoim0-10_20211231_00z_pr.gif){kind=link}
![10-40 cm [4-16 in]](/monitoring-content/sotc/drought/2021/12/rsoim10-40_20211231_00z_pr.gif){kind=link}
![40-100 cm [16-39 in]](/monitoring-content/sotc/drought/2021/12/rsoim40-100_20211231_00z_pr.gif){kind=link}
![100-200 cm [39-79 in]](/monitoring-content/sotc/drought/2021/12/rsoim100-200_20211231_00z_pr.gif){kind=link}
According to the December 31st USDM produced for the USAPI, extreme drought improved to moderate drought in the southern FSM at Kapingamarangi, while moderate drought developed at Wotje (RMI) and abnormal dryness began at Kwajalein (RMI) and Guam. The rest of the USAPI stations were free of drought and abnormal dryness. The National Weather Service (NWS) office in Guam issued two Drought Information Statements (DGT) for drought, one in December (on the 24th) and one in early January (on the 6th) discussing the conditions in the USAPI. Several indicators point to the continuation of La Niña, but a series of westerly wind bursts pulsed across the west Pacific basin during much of the month, bringing several rounds of rain to Kapingamarangi. Community water tanks on the island have filled and were at 100% capacity in late December. Residential water tank levels continue to climb. In late December, crops and vegetation still showed signs of yellowing from previous dry months, but the vegetation showed signs of improvement by early January. Storage in the Majuro reservoir steadily declined during most of December, ending the month at 22.81 million gallons, which is below the 28.8 million gallon threshold for concern.
December 2021 precipitation ranks included several in the top 5 and top 10 driest category, but none of the time periods or any station was driest on record:
- Kwajalein: ninth driest December, fourth driest June-December, and fifth driest May-December (in 70 years of data).
- Nukuoro: ninth driest December (39 years), and sixth driest October-December and September-December.
- Pago Pago: seventh driest December and September-December, and eighth driest August-December and July-December (56 years).
- Kapingamarangi: third wettest December (31 years) but fourth driest August-December and fifth driest July-December and May-December.
- Lukunor: third wettest December (38 years) but sixth driest July-December (25 years).
- Pingelap: ninth driest August-December (36 years).
- Ailinglaplap: fifth driest May-December (37 years).
- Jaluit: third wettest December but ninth driest July-December (38 years).
- Wotje: seventh driest year (January-December) (36 years) as well as April-December, March-December, and February-December.
At the wet end of the scale, it was the wettest year on record at Mili (38 years) and second wettest year at Woleai (26 years).
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 December 2021, July-December 2021 (last 6 months), and January-December 2021 (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 | December 2021 | Jul-Dec 2021 | Jan-Dec 2021 | Period of Record | |||
|---|---|---|---|---|---|---|---|
| Rank | Years | Rank | Years | Rank | Years | ||
| Ailinglaplap | 26 | 38 | 12 | 37 | 25 | 37 | 1981-2021 |
| Chuuk | 55 | 71 | 51 | 71 | 65 | 70 | 1951-2021 |
| Fananu | 5 | 8 | -- | 5 | -- | 2 | 2003-2021 |
| Guam | 25 | 65 | 47 | 65 | 36 | 64 | 1957-2021 |
| Jaluit | 36 | 38 | 9 | 38 | 11 | 37 | 1981-2021 |
| Kapingamarangi | 29 | 31 | 5 | 21 | 6 | 19 | 1962-2021 |
| Koror | 61 | 71 | 65 | 70 | 67 | 69 | 1951-2021 |
| Kosrae | 37 | 54 | 28 | 41 | 30 | 35 | 1954-2021 |
| Kwajalein | 9 | 70 | 8 | 70 | 15 | 69 | 1952-2021 |
| Lukunor | 36 | 38 | 6 | 25 | 18 | 25 | 1981-2021 |
| Majuro | 25 | 68 | 31 | 68 | 59 | 67 | 1954-2021 |
| Mili | 32 | 37 | 34 | 35 | 35 | 35 | 1981-2021 |
| Nukuoro | 9 | 39 | 15 | 38 | 23 | 37 | 1981-2021 |
| Pago Pago | 7 | 56 | 8 | 56 | 13 | 55 | 1966-2021 |
| Pingelap | 17 | 37 | 13 | 36 | 20 | 35 | 1981-2021 |
| Pohnpei | 34 | 71 | 30 | 71 | 61 | 70 | 1951-2021 |
| Saipan | 28 | 34 | 21 | 34 | 19 | 33 | 1981-2021 |
| Ulithi | 33 | 39 | -- | 36 | -- | 34 | 1981-2021 |
| Utirik | -- | 19 | -- | 8 | -- | 4 | 1985-2020 |
| Woleai | 28 | 41 | 27 | 29 | 25 | 26 | 1968-2021 |
| Wotje | 10 | 37 | 11 | 36 | 7 | 36 | 1981-2021 |
| Yap | 54 | 71 | 16 | 71 | 48 | 70 | 1951-2021 |
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 much above average across much of the Southeast region for the month of December, and precipitation was below normal across much the region, with monthly totals ranging from 75 to less than 25 percent of normal. The driest locations were found across much of Virginia, North Carolina, southern Florida and Puerto Rico. Indeed, Charlottesville, VA (1962-2021; 2nd driest) observed only 0.26 inch (7 mm) of precipitation, more than 2.7 inches (69 mm) below normal, and Danville, VA (1916-2021; 4th driest) reported 0.65 inch (17 mm), which was more than 2.4 inches (61 mm) below normal. In contrast, the wettest locations for the month were located across central Georgia and the eastern part of the Florida Peninsula.
Overall drought conditions changed very little in December. At the beginning of the month, a swath of severe drought (D2) stretched from northeastern North Carolina southwestward down to South Carolina, with a pocket of severe drought (D2) near the North Carolina/Virginia border. Moderate drought (D1) ringed the area of severe drought and stretched southward into Georgia. Most of the Southeast region north of Florida had abnormally dry conditions (D0). By the end of the month, the abnormally dry conditions decreased across much of Alabama and Georgia as did the moderate drought. However, the moderate drought expanded northward throughout most of Virginia. Drought conditions remained consistent across Puerto Rico for the month, with much of the island in moderate drought (D1) ringed by abnormally dry conditions (D0) and pockets of severe drought (D2) and extreme drought (D3) across the Virgin Islands. Farmers in the citrus growing region of Florida had to run irrigation due to the dry conditions. Cool season forages and grazing pastures were growing very well with the mild weather conditions in Georgia and Alabama. However, with the daily warmth and cool nights, there were more respiratory problems in livestock. Fungal pathogens and weed control problems were noted as a concern due to the unusually warm December for parts of South Carolina. However, the warm and dry conditions allowed for producers to prepare land for spring and summer crops.
South
As explained by the Southern Regional Climate Center, December 2021 was the warmest winter month on record in the Southern region, with records going back to 1895. The high temperatures were accompanied by below-normal precipitation, particularly in western and southern portions of the Southern region. The region-wide average ranked 14th driest at 1.72 in (44 mm). Substantial portions of western Texas and Oklahoma recorded zero measurable precipitation for the month, and for many of those areas, particularly near Amarillo and Midland, this was the second consecutive month without measurable precipitation.
With the combination of extremely high temperatures and low precipitation, drought conditions worsened across the Southern region. Drought coverage expanded from 41.7% on November 30, 2021 to 62.4% on January 4, 2022, and extreme drought expanded from 0.3% to 15.0% over the same time period. All states except Tennessee had some portions in extreme drought. In western Texas and Oklahoma, the primary drought impacts were to farmers (winter wheat) and ranchers (winter forage, water for cattle), as well as enhanced wildfire risk. Elsewhere, impacts have been relatively minor, but the situation would need to improve fairly quickly over the next two months to avoid substantial agricultural impacts.
Midwest
As described by the Midwest Regional Climate Center, December 2021 was the 4th warmest December on record since 1895 for the Midwest region, while precipitation was variable across the region with statewide totals ranging from 0.53 inch (13 mm) below normal in Iowa to 1.8 inches (46 mm) above normal in Indiana. The most abundant precipitation fell across Minnesota, mostly as snow, where December precipitation was 200-400 percent of normal. The largest precipitation deficits were in western Iowa and northern Missouri where the monthly precipitation was 10-50 percent of normal.
Drought conditions improved slightly in the Midwest during December, although patchy drought and dryness lingered across the northern and western states. The most noteworthy changes happened across northern Minnesota where D3 (extreme drought) was eliminated from the USDM and D2 (severe drought) improved 17 percent. Drought intensified in southern Wisconsin, and abnormal dryness expanded throughout western Missouri. The eastern portion of the region remained drought-free.
Northeast
As explained by the Northeast Regional Climate Center, the Northeast recorded its fifth warmest December since records began in 1895, with the month being another drier-than-normal month. December precipitation ranged from 27 percent of normal in Delaware to 84 percent of normal in New Hampshire.
The USDM released on December 2 showed 1 percent of the Northeast in severe drought, 1 percent in moderate drought, and 8 percent as abnormally dry. Below-normal precipitation in December caused moderate drought to be introduced in eastern West Virginia and eastern Maryland while abnormal dryness expanded in West Virginia, southern Pennsylvania, Maryland, Delaware, and southern New Jersey. In addition, drought and abnormal dryness persisted in northern New England. The USDM from December 28 showed 1 percent of the Northeast in severe drought, 3 percent in moderate drought, and 19 percent as abnormally dry.
High Plains
As summarized by the High Plains Regional Climate Center, above-normal temperatures prevailed throughout most of December and precipitation varied across the High Plains for the month. The northern plains, including drought-stricken parts of North Dakota and western Colorado, observed above-normal precipitation for the month. In the southern High Plains, below-normal precipitation was recorded, with areas in Kansas and eastern Colorado receiving less than 5 percent of their normal precipitation. This precipitation gradient resulted in some locations ranking in the top 10 wettest and driest December on record. Wichita, KS observed their driest December on record with 0.01 inch (0.25 mm) of precipitation. Chadron, NE tied with 2010 and other years for the driest December on record, observing a trace of precipitation. While the southern High Plains observed below normal precipitation, on December 15th an intense derecho moved through the region impacting Colorado, Nebraska, and Kansas with damaging winds, rain, tornadoes, and dust.
The trend of above-normal temperatures and dryness across the southern High Plains continued through the month of December. Drought conditions continued their spread and intensified in Kansas, Colorado, and Nebraska while the Dakotas observed improvements. Despite the intensification of drought conditions this past month, the region remained free from exceptional drought (D4) conditions. Kansas experienced the most significant degradations to drought conditions this past month. The amount of the state covered in moderate drought (D1) to D4 increased from 19 percent to over 50 percent during the course of the month. Abnormally dry (D0) conditions now also cover 73 percent of the state. In Colorado, the entire state is now engulfed by D1 to D3 conditions. Despite minimal change to the percentage of the state in severe drought (D2), conditions in the western part of the state improved while the eastern parts declined. Above-normal precipitation in the eastern Dakotas led to the reduction of abnormally dry and drought conditions. Throughout the rest of the region, other improvements and degradations were observed. According to the U.S. Monthly Drought Outlook for January, drought improvement is likely in western Wyoming.
West
As described by the Western Regional Climate Center, many regions in the West experienced stormy weather during December 2021, bringing welcome precipitation and near-to-slightly below average temperatures. December began with low-to-no snow throughout most major western U.S. mountains. Later in the month, heavy and sustained snowfall brought significant snowpack gains to California, Nevada, Oregon, Utah, Wyoming, Montana, and Washington. Lower elevations received beneficial rainfall. As a result, drought conditions improved across much of the West, especially in central Utah, coastal Oregon, central and southern California, northern Idaho, and western Montana. In the Desert Southwest, southern Nevada and Arizona received above-average precipitation that improved drought conditions. Continued warm and dry conditions maintained and exacerbated drought in New Mexico. Wetter-than-average conditions in Hawaii led to notable drought improvement. Dry conditions prevailed in New Mexico. Clayton, NM recorded no measurable precipitation during December, tying its driest December in 112 years of records.
Persistent low pressure in the far western U.S. favored near- to below-average temperatures. But temperatures were well-above average in the desert Southwest as a result of persistent ridging. With 76 years of records, Roswell, NM set a December heat record with mean temperatures of 50 F (10 C), which is 8 F (4.8 C) above normal. Tucson, Arizona, where record keeping began in 1930, experienced its second warmest December with a mean temperature of 57.2 F (14 C), which is 4 F (2.4 C) above normal.
Sea surface temperatures (SST) in the vicinity of Hawaii remained 0.5-1 C above average. La Niña-like atmosphere-ocean conditions persisted further south in the tropical Pacific with strong anomalous tropical easterly winds and upwelling equatorial Kelvin waves driving cold (2-3 C below average) SST anomalies along the equator. Kahului, HI (Maui) tied its 14th warmest December since records began in 1954 with an average temperature of 74.5 F (23.6 C; 0.1 F (0 C) below normal). Above-normal precipitation brought drought improvement to all islands, especially Maui and Moloka'i. On Maui, Kahului observed 7.45 in. (189 mm) of precipitation, good for its 5th wettest December and 266% percent of average.
Alaska experienced an eventful December with a range of weather and climate extremes. On December 26, Kodiak Harbor observed a maximum temperature of 67 F (19.4 C), the highest December temperature recorded anywhere in Alaska. With 78 in. (1,981 mm) of snowfall, Denali National Park observed its snowiest December and deepest total snow depth (60 in. (1,524 mm)) since record-keeping began in 1923. Western Alaska was wetter than normal. Nome measured the most December precipitation since records began in 1900 with 3.92 in. (99 mm) of precipitation falling (373% of normal). Southeastern Alaska was drier than normal. Cordova recorded its lowest December precipitation since records began in 1909, measuring 1.87 in. (47 mm; 23% of normal). Bering Sea ice achieved its highest mean extent since 2012.