US Extreme Weather and Climate Change Dashboard
Variables on this page
Every variable below is evaluated over a full reliable-trend window against this site's combined "detected change" standard (IPCC's likelihood criterion plus a magnitude-vs-variability check -- see the homepage or Methodology for the full definitions). Shown as alternative ways of characterizing this same phenomenon -- some from independent sources, others a different construction on the same underlying data (each variable's own note says which).
Palmer Drought Severity Index (PDSI), 1895–2026
National (contiguous 48 states) monthly PDSI from NOAA nClimDiv — a single meteorological/soil-moisture index, negative for dry conditions and positive for wet conditions. This is the long-record context layer alongside the US Drought Monitor panel below; full methodology on the Methodology page.
Source: NOAA NCEI nClimDiv (PDSI)
Shading shows dry months (below the zero line) versus wet months (above it) so the sign of PDSI is visible at a glance, not just readable from the number. The 2026 portion of the line reflects only the months observed so far this year and is not a full-year figure yet (see the Methodology page).
Drought
WeeklyUS Drought Monitor, weekly national area by severity category. Unit: % of CONUS.
USDM's whole record is used as the reliable window — 2000 is the record start, not a sub-window found within the data, so there's no earlier period to exclude here. USDM's native categories (D0 abnormally dry through D4 exceptional drought) are already cumulative ("this severity or worse") in the source data, not raw per-band values — D2+ is the level selector's default, chosen as the closest USDM analogue to a "1-in-10 or worse" severity cutoff (full rationale on the Methodology page), but every category is selectable.
Source: US Drought Monitor (USDM)
Computing trend…
Drought — SPEI
MonthlySPEI computation (Hargreaves PET, log-logistic standardization) -- a second, independently-derived drought index alongside PDSI, using a different PET formula specifically so a drought finding can be checked against a documented critique that PDSI's formula overstates warming-driven drying. Unitless; negative values are dry, positive are wet. Unit: SPEI.
Uses the same GHCN-Daily HCN station network that shows a reliable trend from ~1895; station count is exported per month so a thin-network period is visible rather than hidden. Uses a different, more defensible PET formula than PDSI (Milly & Dunne 2017) -- the two indices meaningfully diverge for 2021-2025 (PDSI strongly negative, SPEI only mildly so), a real finding disclosed on the Methodology page, not smoothed over.
Source: NOAA GHCN-Daily (temperature + precipitation), SPEI computed in-house
Computing trend…
Drought — Agricultural (Soil Moisture)
Monthly% of 3,308 CONUS land cells (0.5° grid) whose 3-month mean soil moisture falls at a selectable USDM-equivalent severity level or worse against that cell's own same-calendar-month history — the same modeled-soil-moisture-percentile approach USDM uses as one of its standing inputs, run as its own series so one USDM input is visible on its own. Unit: % of CONUS land area.
A rainfall deficit becomes an agricultural drought only once the soil store draws down, so this series lags and damps precipitation rather than tracking it. CPC calculates soil moisture with a one-layer "leaky bucket" model driven by observed precipitation and temperature, rather than measuring it. That gives a single column of soil water instead of separate surface and root-zone depths, and makes the series a model estimate constrained by observations, not an observation. Read the trend with the record's start in mind: the two driest years here are 1956 and 1954, so Sen's slope runs +0.04 points/decade over the full 1948 record but +1.96 starting from 1990 — cutting the 1950s Southern Plains drought is what produces a drying trend, which is why the full record is used. See Methodology.
Source: NOAA CPC Monthly Soil Moisture v2 (Fan & van den Dool 2004), NOAA PSL
Computing trend…
Drought — Hydrologic (Low-Flow)
WeeklyThe mirror image of the Flooding page's high-flow index: % of HCDN-2009 reference gauges currently at or below the historical 10th percentile for the day of year -- a runoff-based drought signal, distinct from PDSI/USDM/SPEI's precipitation/soil-moisture basis. Unit: % of reference gauges below threshold.
Shares the high-flow index's 1957 reliable-trend window (the same underlying gauge-network coverage finding applies to either tail). 1934/1931 rank as the two driest years in the full record, and 1988/2012 both land in the reliable window's top 10.
Source: USGS NWIS daily discharge, HCDN-2009 reference gauges
Computing trend…
Four measures of drought, one page
"Drought" names several different deficits, and this page measures each separately rather than folding them into a single number. US Drought Monitor is the operational composite. SPEI is a rainfall deficit adjusted for evaporative demand. Soil moisture is agricultural drought — the water actually available to crops. Hydrologic low flow is a runoff deficit at reference stream gauges. They run on very different records: 26 years for USDM, 78 for soil moisture, 69 for low flow, and 131 for SPEI.
None of the four shows a detected increase. Applying this site's detection standard — a statistically significant Mann-Kendall trend that also exceeds the series' own variability — SPEI returns p=0.23 over 131 years, soil moisture p=0.89 over 78 years, and hydrologic low flow p=0.14 over 69 years. USDM's own record, starting in 2000, is shorter than the 30-year minimum this site requires before drawing a trend line at all. Four independent measurements of four different deficits, over records up to 131 years, and none of them separates a trend from the noise.
The soil-moisture series is the clearest illustration of why the start year matters. Its two driest years are 1956 and 1954 — the 1950s Southern Plains drought — with 2021, 2002, 1977, 2022 and 2012 behind them. Because the dry extreme sits early in the record, Sen's slope runs +0.04 points per decade over the full 1948 record but+1.96 starting from 1990. Cutting the 1950s is what produces a drying trend, which is why the full record is used here. See the Methodology page.