The European Heat Tracker estimates how Europe's heat today compares with the historic climate, and how many people are exposed to it. It combines a high-resolution population grid with the latest weather model data to produce per-country and continent-wide figures. The focus is today: the headline figures and the map describe the current day, refreshed through the day as new model runs arrive.
The map offers four views — Difference from average (today vs. the 1961–1990 climate, the default), Temperature, Feels like, and Heat stress (UTCI). Three headline figures summarise the day: the area-mean temperature anomaly, the number of people in "uncommonly hot" conditions, and the number at 30 °C or more.
Population figures come from the GHS-POP R2023A dataset published by the European Commission's Joint Research Centre (JRC). This is a global population grid at approximately 1 km² (30 arc-second) resolution, based on the 2020 population epoch.
We aggregate the raw 1 km² cells onto a 0.0625° latitude/longitude grid (1⁄16°, roughly 5 × 7 km at European latitudes — close to ICON-EU's ~6.5 km resolution), resulting in approximately 175,000 grid cells covering the European continent. Each cell stores the total population count summed from the underlying high-resolution raster, preserving real population density variation between urban and rural areas.
Weather data comes from DWD ICON-EU, the operational numerical weather prediction model of Germany's national meteorological service (Deutscher Wetterdienst). ICON-EU covers Europe at a native resolution of approximately 6.5 km and is published as open data in GRIB2 format through the day. Our pipeline ingests the most recent available run every 3 hours; because DWD publishes each run roughly 3 hours after its initialisation time, the model run shown in the map legend always trails the wall clock by a few hours.
For each grid cell we compute three heat indicators:
GRIB2 files are downloaded, regridded to the population grid via bilinear interpolation, and stored in SQLite. The pipeline includes up to 72 hours of forecast data.
Two of the three headline figures compare today against a historic climate baseline built from E-OBS, the ECA&D / Copernicus gridded daily station-observation product for Europe (~0.1°). For each grid cell we compute, over the 1961–1990 reference period and a ±15-day window around each calendar date, the mean and the 90th percentile of daily-mean temperature.
Why the 1961–1990 baseline? It is the WMO / IPCC reference period for climate-change assessment, used by DWD, the Met Office and the EEA, and it conveys the full warming signal more honestly than the current 1991–2020 operational normal — which is itself already shifted by warming. The trade-off is that it runs roughly 1 °C cooler than today's normal, so a reading near 0 °C here is actually slightly below what is typical now, and our anomalies sit about 1 °C warmer than live trackers that use the 1991–2020 baseline (such as Copernicus Climate Pulse) or 1979–2000 (ClimateReanalyzer). It also means that "uncommonly hot" is uncommon relative to 1961–1990 — not necessarily rare by today's standards.
A grid cell is classified as affected when its selected indicator meets or exceeds the active threshold. Default thresholds:
Thresholds can be adjusted per-indicator using the ⚙ settings cog next to the map-view switch. They affect only the "affected" highlighting on the map and the tooltip marker — the headline figures are independent of them.
"Today" is the eight 3-hourly snapshots of the current UTC day (00–21 UTC). Early hours are recent analysis/short-range forecast; later hours are forecast from the most recent run — so the day's figures blend observed-so-far with forecast-for-tonight, and shift slightly as new runs come in.
The 30 °C or more count is a union: a cell counts if its temperature reaches the threshold in any snapshot today (a daily-maximum view). The anomaly and "uncommonly hot" figures instead use each cell's daily mean (the average of the day's snapshots), which is the right basis for comparing against the daily-mean climatology. Per-country figures aggregate the same cells within each country.
The DWD data pipeline runs every 3 hours, aligned with DWD's model run schedule. Each run downloads the latest analysis and forecast fields, creates new snapshots in the database, and makes data available immediately to the web app.