Reading the US Drought Monitor

The US Drought Monitor is a weekly map that classifies drought across the United States into five categories. D0, abnormally dry, marks an area entering or recovering from drought. D1 is moderate drought, D2 severe, D3 extreme, and D4 exceptional — the most intense category, associated with widespread water shortages and major agricultural losses. The map has been produced weekly since 1999.

The categories are not output from a single dataset. Each week, a map author blends many indicators — precipitation, soil moisture, streamflow, reservoir levels, vegetation health — with local input from hundreds of climate and water experts across the country. That combination of objective data and expert judgment is deliberate: drought shows up differently in a rangeland county than in a snow-fed basin, and no single index captures both.

For operators, the categories translate into impact statements. Moderate drought is commonly associated with some crop and pasture damage and developing water shortfalls; extreme and exceptional drought describe major, broad-scale impacts. County- and state-level statistics summarize how much of an area sits in each category each week, and week-over-week changes show whether conditions are building or easing.

Those statistics are most useful as a trend, not a verdict. A twelve-week series showing the percent of a state in D2 or worse tells you whether the region is sliding deeper or recovering — which is exactly how the national statistics are presented in monitoring dashboards, including on our EarthView page. The weekly percent-area numbers matter for programs too: drought categories are frequently used as eligibility or trigger references in assistance and rebate programs.

The map's limits are worth respecting. It is a weekly, large-area product: a county rated D0 can still contain a property whose root zones are severely dry, and a D2 county can contain well-watered turf. The Drought Monitor describes the region; measurements describe the property. Used together — regional context from the map, local truth from the ground — they answer different halves of the same question.