- Based on the Palmer Drought Index, severe to extreme drought affected about 11 percent of the contiguous United States as of the end of March 2015, an increase of about 3 percent from last month. About 1 percent of the contiguous U.S. fell in the severely to extremely wet categories.
- About 21 percent of the contiguous U.S. fell in the moderate to extreme drought categories (based on the Palmer Drought Index) at the end of March.
- 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 decade 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), about 36.8 percent of the contiguous U.S. (CONUS) (about 30.8 percent of the U.S. including Alaska, Hawaii, and Puerto Rico) was classified as experiencing moderate to exceptional (D1-D4) drought at the end of March.