National Climatic Data Center, 13 January 2005

• severe to extreme drought affected about 4 percent of the contiguous United States as of the end of December 2004, about the same as last month
• about 6 percent 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 previous two decades (1980s and 1990s) were characterized by unusual wetness with short periods of extensive droughts, whereas the 1930s and 1950s were characterized by prolonged periods of extensive droughts with little wetness (see graph below right)
• about 23 percent of the contiguous U.S. fell in the severely to extremely wet categories at the end of December
• a file containing the national monthly percent area severely dry and wet from 1900 to present is available
• 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 in files having names that start with "drd964x" and ending with "txt" (without the quotes).