Explaining Drought Category Maps

Drought categories are typically based on percentile statistics, where the percentile indicates the number of percent of measurements under the given value. For example, a one month precipitation total in the 5th percentile indicates that only 5% of all available one month precipitation totals are lower than the observed month. The drought categories for the drought blends, Standardized Precipitation Indices (SPI) and the Evaporative Demand Drought Index (EDDI) are all based on the same percentile ranges and categories used for the US Drought Monitor.

Please refer to the National Drought Mitigation Center for more information on the drought classifications used in the U.S. Drought Monitor.

Category	Description	Possible Impacts *Impacts vary by state	Range
D4	Exceptional Dry	Exceptional and widespread crop/pasture losses Shortages of water in reservoirs, streams, and wells creating water emergencies	0 to 2
D3	Extreme Drought	Major crop/pasture losses Widespread water shortages or restrictions	2 to 5
D2	Severe Drought	Crop or pasture losses likely Water shortages common Water restrictions imposed	5 to 10
D1	Moderate Drought	Some damage to crops, pastures Streams, reservoirs, or wells low, some water shortages developing or imminent Voluntary water-use restrictions requested	10 to 20
D0	Abnormally Dry	Going into drought: short-term dryness slowing planting, growth of crops or pastures Coming out of drought: some lingering water deficits pastures or crops not fully recovered	20 to 30
	Neither wet or dry	N/A	30 to 70
W0	Abnormally Wet	N/A	70 to 80
W1	Moderate Wet	N/A	80 to 90
W2	Severe Wet	N/A	90 to 95
W3	Extreme Wet	N/A	95 to 98
W4	Exceptional Wet	N/A	98 to 100

For technical questions or questions about the National Integrated Drought Information System (NIDIS), the U.S. Drought Monitor, or the Drought.gov website, email drought.portal@noaa.gov or visit our Contact Us page.

Explaining Drought Category Maps

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