Drought
Drought Monitor Explained: D0 to D4 Categories and What They Mean
How drought categories work, what D0 through D4 mean, and why drought is measured with more than just rainfall totals.
Quick answer: The Drought Monitor ranks drought from abnormally dry to exceptional drought using precipitation, soil moisture, streamflow, vegetation, impacts, and expert analysis.
The category scale
D0 means abnormally dry. D1 through D4 describe increasing drought severity, ending with exceptional drought.
The categories help communicate impacts, but local conditions can vary within a county or region.
More than rain
Drought depends on rainfall deficits, heat, evaporation, soil moisture, snowpack, groundwater, streamflow, and demand.
A hot windy pattern can worsen drought even without record-low rainfall.
Why it matters
Drought affects agriculture, water supply, wildfire risk, ecosystems, navigation, and outdoor restrictions.
Recovery can take much longer than one rainy week if deficits are deep.