How to read the U.S. Drought Monitor

The U.S. Drought Monitor is the most cited agricultural climate product in the United States, and it is easy to quote wrongly in two specific ways.

One: categorical and cumulative are both published

The service offers area statistics in two forms.

Categorical means what it says: the share of the state in D1 and no worse. The categories partition the state, so they sum with the no-category share to 100%.

Cumulative means D1 or worse. Each category includes every more severe one, so the shares nest and sum to far more than 100%.

For Nebraska on the map of 25 February 2025, the D1 figure is 43.09% in categorical form and 90.79% in cumulative form. Same map, same week, same state. A brief that took the cumulative number and described it as "43% of Nebraska in moderate drought" would be wrong twice: wrong figure, wrong category meaning.

There is a reliable way to tell which one you have without asking: add the categories together, including the no-category share. Categorical sums to 100. Cumulative does not come close. AgricultureID ingests the categorical form and validates that sum on all 7,000 state-weeks it holds, which is how a mislabelled ingest would be caught rather than published.

Two: D0 is not drought

The categories run D0 to D4. D0 is abnormally dry, and the Drought Monitor describes it as a precursor to drought and as a category areas pass through while recovering. It is not drought.

Across the fifty states in the week of 25 August 2026, counting D0 as drought would add 22.7 percentage points to the average state's drought figure. That is not a rounding difference; it is a different map. California in that week sits at 13.9% in drought and 51.3% in D0 — fold them together and you have described a state in widespread drought when the assessment says the opposite.

And a third: a map has an expiry

Each weekly map states the week it is valid for. Outside that window it is history — accurate about its week, silent about now.

This sounds obvious and is the most common failure in drought reporting: a figure lifted from a map published in July, presented in September as the current state of a drought. AgricultureID's climate layer will only return an assessment as current if the reference date falls inside that map's own validity window, and a date outside every window returns nothing rather than the nearest map.

What it is, finally

The Drought Monitor is an assessment. Each map is drawn by a rotating author who weighs several drought indicators together with reports from local observers. It is authoritative and it is a judgement — not an instrument reading and not a model output. Reporting it as a measurement overstates its precision; dismissing it as an opinion understates its standing. It is neither.