Drought, snow & water rights
How to read the US Drought Monitor: D0 to D4
D0 abnormally dry, D1 moderate, D2 severe, D3 extreme, D4 exceptional. What each US Drought Monitor class means, and why percent in drought starts at D1.
Updated Aug 13, 2026
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The US Drought Monitor is a weekly map that grades drought in five steps, and the letter codes are the whole vocabulary.
- D0, abnormally dry. A watch category, not drought yet. Going in, it is dryness slowing planting and crop growth. Coming out, it is the deficits a wet spell has not made up.
- D1, moderate drought. Some damage to crops and pasture. Streams, reservoirs or wells running low, and voluntary conservation requests.
- D2, severe drought. Crop or pasture losses likely. Water shortages common, restrictions imposed.
- D3, extreme drought. Major crop and pasture losses, with widespread water shortages or restrictions.
- D4, exceptional drought. The worst rating. Exceptional and widespread crop and pasture losses, and shortages in reservoirs, streams and wells that create water emergencies.
A new map comes out every Thursday morning, produced jointly by the National Drought Mitigation Center, the USDA and NOAA.
What percent in drought actually counts
The scale is cumulative in how it gets reported. When this site says a state is a certain percent in drought, that is the share of its area at D1 or worse, so D0 alone does not count as being in drought. Watch for that when you compare two sources. A figure that folds in D0 will always look worse than one that starts at D1, and in a marginal year the two can tell opposite stories about the same state.
The Thursday release and its lag
The map is released Thursday but the data cut off the previous Tuesday, so it always trails the weather by a few days. A big storm that lands Wednesday shows up in next week's map, not this one. That lag matters when conditions are moving fast. The Monitor is a considered weekly read, not a live sensor.
It is judgment, not a single formula
The Monitor is not the output of one equation. Authors weigh many inputs, precipitation, streamflow, soil moisture, snowpack and reservoir data, and then apply expert judgment, rotating the authorship each week. That is a strength, because no single index captures drought, and a limitation, because there is a human read in the loop.
What it triggers, and what it does not measure
The categories move money. USDA disaster designations, Farm Service Agency emergency loan eligibility and some insurance and relief provisions are tied to Monitor thresholds. Check the current program rules with the agency, because the specific triggers change. Just as important is what the Monitor does not do. It is not a groundwater gauge and not a reservoir gauge. A basin can show low drought on the map while its reservoirs are still drawn down from prior years, so read it alongside the storage pages, not instead of them.
Worked example: reading one state's recent weeks
The table above shows California's drought coverage now against a week ago, a month ago, a year ago and the five-year median for this date, in percentage points. Read the week-over-week line for direction, the year-over-year line for how this season compares, and the five-year line for whether the state sits above or below its own normal. A state can be heavily in drought yet still be below its five-year normal, which is why we report the change in points rather than a single scary headline number.
Now look at the live data
Common questions
What is the difference between D0 and D1 drought?
D0 is abnormally dry, a watch category that flags dryness before it becomes drought. D1 is moderate drought, the first step that actually counts as drought. When coverage is reported as a percent in drought, it usually means D1 or worse, so D0 area is excluded.
What does D2 drought mean?
D2 is severe drought, the middle rung of the five-step scale. Crop or pasture losses are likely, water shortages are common, and water restrictions are typically imposed. It sits one step above D1 moderate drought and one below D3 extreme drought.
How often is the US Drought Monitor updated?
Once a week. A new map is released every Thursday morning, using data through the previous Tuesday, so it lags fast-moving weather by a few days.
Is the Drought Monitor a forecast?
No. It describes current and recent conditions based on observed data and expert judgment. It does not predict future drought. Separate seasonal outlooks handle forecasting.
Does the Drought Monitor measure reservoirs or groundwater?
Not directly. It considers many indicators but it is not a storage gauge. A region can read low on the map while its reservoirs are still low from earlier dry years, so pair it with the reservoir and streamflow data.