North American Drought Monitor Indices
Canada is not included in the contour maps because of the limited number of climatological stations currently available. Until sufficient data are made available to increase the station density so that contours can be more accurately drawn, Canadian data will be provided only on the dot maps. The maps are based on station data for Canada, Mexico, and Alaska, and on climate division data for the contiguous U.S. plotted on the divisions' center points.
The Percentage of Long-Term Average Precipitation is a viable indicator of drought conditions. Long-term average precipitation for station or climatic division has been calculated over a 1951 to 2001 base period. The following maps show the percentage of these averages that has fallen in periods ranging from the past month to the past five years.