Statistics for the most recent period/season are computed from a fraction of the U.S. which has data available at that time. Extreme percentage values can and will likely change as final quality controlled data become available and fill in the data gaps.

As of September 2005, the 4th and 5th indicators are computed with data from one station per each grid box rather than multiple stations. This was done to eliminate many of the artificial extremes which resulted from a changing number of available stations over time. Therefore, the percentages calculated after to the changes implemented in September 2005 will likely be significantly different than the those calculated prior to the changes.

As of December 2005, landfalling wind speeds in the sixth indicator are determined using the following logic:

1. For landfalls prior to 1915: Use wind speed observation prior to landfall as landfalling windspeed.
2. For landfalls from 1915 to 1930: Use wind speed observation prior to landfall if observation was at 12Z. Otherwise use midpoint windspeed value from assigned landfalling Saffir-Simpson Scale.
3. For landfalls from 1931 to 1979: Use wind speed observation prior to landfall if observation was at either 0Z or 12Z. Otherwise use midpoint windspeed value from assigned landfalling Saffir-Simpson Scale.
4. For landfalls from 1980 to the present: Use estimated landfalling windspeed as reproted in the Tropical Cyclone Reports issued by the National Hurricane Center.