Drought

Drought on TerraPulse is organized as a YearLocationdex — a single spine that indexes measured drought severity across every U.S. county, week by week. Each entry is an assessed condition on the ground, not a forecast.

The dexes

Drought lives in two YearLocationdexes, both organized county × week:

Rather than one slot per event, a drought dex is a single organizing spine that resolves drought severity by place and time — the weekly U.S. drought classification for each county, building a continuously updated national map. The spine grows as each new weekly assessment is published.

The two differ in how finely they cut the same assessments. drought answers whether a county was in moderate-or-worse drought (D1 and above) in a given week. drought_category keeps every category separately, so it can answer how deep the drought went and how long it stayed there — the worst category reached, the share of the county in each, and the length of the longest consecutive run at D2 or worse. It covers 3,211 counties across 49 states, the District of Columbia and Puerto Rico, 2000 through 2024 — 4.19 million county-weeks. Connecticut is the one gap: it retired its counties for planning regions, and the USDM county series does not carry it.

That per-category detail is what makes the dex usable for agriculture. USDA's Livestock Forage Program keys its payments to specific drought thresholds — a county qualifies on reaching D2 for long enough, or D3 at all — so drought_category records, for each county and year, which of those thresholds the measured record actually crossed.

Provenance

Every value traces to the U.S. Drought Monitor (USDM), delivered via NOAA NCEI and the CDC environmental-health tracking pipeline. The USDM is the authoritative weekly drought assessment for the United States, produced from measured precipitation, soil-moisture, and streamflow conditions. That source is registered against the dex, so any record on TerraPulse carries a direct line back to its originating USDM release.

What's in a record

Each entry carries:

• Location — county and state
• Week — the USDM assessment week
• Severity — drought category from D0 (abnormally dry) through D4 (exceptional drought)
• Extent — the share of the area in each category

In drought_category, each county-week additionally carries the worst category reached, the running length of the current D2-or-worse spell, and whether that week's record crosses the Livestock Forage Program thresholds.