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🌡️ Heat & Health
At 30°C, physiological strain begins in unacclimatized Europeans
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Heat & Health
At 30°C, physiological strain begins in unacclimatized Europeans
| Temperature | Health impact | Risk groups |
|---|---|---|
| ≥ 30°C | Physiological strain begins; dehydration risk | Elderly, outdoor workers |
| ≥ 35°C | Heat cramps, exhaustion; cognitive impairment | All, especially those without AC |
| ≥ 38°C | Heat stroke risk; excess cardiovascular mortality | High risk for over-65s, infants |
| ≥ 40°C | Life-threatening; organ failure possible | Everyone at risk |
Europe's 2003 heatwave caused approximately 70,000 excess deaths. The 2022 heatwave was associated with over 60,000 excess deaths across Europe (Ballester et al., 2023, Nature Medicine). Urban heat islands can add 5–10°C above surrounding rural temperatures.
📐 How we measure heat
Three indicators from direct weather data to perceived comfort
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How we measure heat
Three indicators from direct weather data to perceived comfort
Air Temperature (2m) — The standard meteorological measurement at 2 metres above ground. Simple and universally understood.
Feels Like (Steadman apparent temperature) — Accounts for humidity and wind speed. In humid conditions, feels-like can be significantly higher than air temperature because sweat evaporates less efficiently. Formula: AT = Ta + 0.33×e − 0.70×ws − 4.00 (where e = vapour pressure, ws = wind speed).
UTCI classification (Bröde et al., 2012):
| UTCI range | Stress category |
|---|---|
| 9 – 26°C | No heat stress |
| 26 – 32°C | Moderate heat stress |
| 32 – 38°C | Strong heat stress |
| 38 – 46°C | Very strong heat stress |
| > 46°C | Extreme heat stress |
UTCI (Universal Thermal Climate Index) is the most physiologically comprehensive indicator: it accounts for air temperature, radiation, wind, and humidity. Our default threshold of 26°C marks the onset of moderate heat stress.
🗄️ Data & methodology
Weather from DWD ICON-EU, population from Eurostat/JRC grid
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Data & methodology
Weather from DWD ICON-EU, population from Eurostat/JRC grid
- Weather model: DWD ICON-EU — Germany's national meteorological service operational NWP model. Native resolution ~6.5 km, regridded here to ~14 km for performance.
- Update schedule: DWD runs ICON-EU 4× per day (00, 06, 12, 18 UTC). Our pipeline fetches new data within ~3 hours of each model run.
- Forecast horizon: Up to 72 hours of forecast data is stored alongside analysis fields, enabling the "Next 3 days" view.
- Population grid: Eurostat / JRC GEOSTAT 2018 population grid at 1 km resolution, aggregated to the weather grid. Each grid cell is weighted by the number of residents.
- Affected population: For a given time range, a person is counted as "affected" if they live in a cell where the selected indicator exceeded the threshold in at least one snapshot during the period.
- UTCI calculation: Computed from 2m temperature, dewpoint (for vapour pressure), 10m wind speed, and mean radiant temperature (approximated from downwelling shortwave radiation).
📚 Scientific references
Sources behind our thresholds, methods, and health context
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Scientific references
Sources behind our thresholds, methods, and health context
- Bröde, P. et al. (2012). Deriving the operational procedure for the Universal Thermal Climate Index (UTCI). International Journal of Biometeorology, 56(3), 481–494. doi:10.1007/s00484-011-0454-1
- Ballester, J. et al. (2023). Heat-related mortality in Europe during the summer of 2022. Nature Medicine, 29, 1857–1866. doi:10.1038/s41591-023-02419-z
- EEA Climate-ADAPT. Heat and health. European Environment Agency. climate-adapt.eea.europa.eu
- WHO Regional Office for Europe. (2008). Heat–health action plans: guidance. World Health Organization. who.int/europe
- Steadman, R.G. (1994). Norms of apparent temperature in Australia. Australian Meteorological Magazine, 43(1), 1–16.
- EEA (2023). Universal Thermal Climate Index (UTCI) days indicator. eea.europa.eu
- DWD Open Data — ICON-EU GRIB2 data. opendata.dwd.de