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.
*Impacts vary by state
||0 to 2|
||2 to 5|
||5 to 10|
||10 to 20|
Going into drought:
Coming out of drought:
|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 email@example.com or visit our Contact Us page.