Global Extreme Weather and Climate Change Dashboard
Heat Waves
Extreme temperatures -- heat and cold combined -- account for about 2% of global weather/climate economic losses but about 21% of deaths, 1980-2025 (see Loss Normalization), a disproportionate human toll relative to the direct dollar cost. Station-based heat extremes here come from GHCN-Daily's global GSN network (about 991 stations, 164 countries): a station-relative heat wave event count, a magnitude index scoring each year's most severe heat wave, and three standard ETCCDI/CLIMDEX indices (TXx, WSDI, TN90p). The reliable trend window starts in 1949; a separate Europe-only index applies the same method to the one continent with a station network dense enough to support it.
Summary Judgment
All 4 independently-constructed heat metrics show a detected increase since 1949 -- a clean match to AR6's "virtually certain" finding, not just one headline number agreeing by chance.
IPCC finding (AR6 WG1 SPM A.3.1): "It is virtually certain that hot extremes (including heatwaves) have become more frequent and more intense across most land regions since the 1950s." — see the full Detection & Attribution comparison for every phenomenon this site tracks.
Variables on this page
Every variable below is evaluated over a full reliable-trend window against the 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 note says which).
Heat Waves — Global Heat Wave Index
AnnualGlobal heat wave index: unweighted mean event count across qualifying GSN reference stations worldwide, using the same station-relative (90th-percentile-of-its-history) detection as the US dashboard's heat wave variable. Unit: events per station per year.
Source: NOAA GHCN-Daily, GCOS Surface Network (GSN) stations
Computing trend…
Averages event counts across qualifying GSN stations worldwide. A separate Europe-only index and North America index apply the same method to each continent's own station network. See Methodology for station-network coverage and reporting-lag detail.
Heat Waves — Magnitude Index (HWMId-style)
AnnualA magnitude-integrated companion to the event-count index above -- how intense and how long each year's most extreme heat wave was, not just how many qualified. HWMId-style (Russo et al. 2014/2015): each hot day's excess above threshold is scaled and summed over the event's full duration, so one severe multi-week heat wave scores far higher than several short mild ones the count-based index would treat as equivalent. Unit: magnitude index (dimensionless).
Source: NOAA GHCN-Daily, GCOS Surface Network (GSN) stations
Computing trend…
Scores each year's most severe heat wave by combining its duration and intensity above threshold, distinct from the event-count index above, which counts qualifying events without weighting their severity. See Methodology for the construction and the 2010 Russian heat wave validation check.
Heat Waves — TXx (Annual Max Temperature)
AnnualIPCC AR6/ETCCDI standard TXx -- the single hottest daily high temperature observed each year, no percentile threshold involved. A standard, independently-verifiable complement to the bespoke heat wave index above. Unit: °C (annual max daily high).
Source: NOAA GHCN-Daily, GCOS Surface Network (GSN) stations
Computing trend…
Reports the single hottest daily high temperature observed each year, averaged across qualifying stations, with no percentile threshold or base period. See Methodology for validation against 2024's global temperature record.
Heat Waves — WSDI (Warm Spell Duration Index)
AnnualETCCDI/CLIMDEX standard WSDI -- annual count of days in a run of 6+ consecutive days above a station's fixed-base-period (1961-1990) 90th percentile. Unit: days per year.
Source: NOAA GHCN-Daily, GCOS Surface Network (GSN) stations
Computing trend…
Counts days in a run of 6 or more consecutive days above each station's 1961-1990 base-period 90th percentile. See Methodology for the ETCCDI/CLIMDEX definition.
Heat Waves — TN90p (Warm Nights)
AnnualETCCDI/CLIMDEX standard TN90p -- percent of days with an overnight low above a station's fixed-base-period (1961-1990) 90th percentile. NCA5 flags nighttime-low warming as a distinct, high-confidence signal, not a redundant restating of TXx. Unit: % of valid days.
Source: NOAA GHCN-Daily, GCOS Surface Network (GSN) stations
Computing trend…
Reports the percentage of days with an overnight low above each station's 1961-1990 base-period 90th percentile. See Methodology for the ETCCDI/CLIMDEX definition.