Heat risk depends on more than air temperature. Humidity, sun and wind can make outdoor conditions far more dangerous than the thermometer suggests. We map that with WBGT, a standard heat-stress index, using climate-model and reanalysis data.
The interactive map shows indicative outdoor heat-stress patterns worldwide at roughly 25 km resolution, for present-day baseline conditions and future scenarios out to 2060. It is free to use. For organisations with many sites, the same data is also available as a bulk screening report or an API. See For business.
How these heat-stress estimates are produced, how they were checked against real observations, and what they can and cannot be used for.
WBGT (Wet Bulb Globe Temperature) is a physics-based heat-stress index. It combines temperature, humidity, wind and solar radiation into a single number. ISO 7243 uses it as the standard measure of how dangerous heat is for people working or exerting themselves outdoors. It covers far more than air temperature alone.
WBGT is computed from CMIP6 climate-model fields and ERA5 reanalysis, run through the Liljegren physics engine. Corrections are applied at each location for elevation, surface roughness (which affects wind) and albedo (reflectivity). The present-day baseline is an ERA5 climatology for 1991 to 2020. Projections use a delta method that combines ERA5's observational accuracy with the climate-model change signal.
The approach was checked against 211 weather stations across 115 countries. The forcing error, re-derived on the fixed physics engine, is −0.899 °C, and a constant +0.899 °C bias correction is applied. Two caveats apply to that number:
Use this to prioritise further assessment. It helps identify which locations and scenarios need a closer look on the ground. Do not use it alone for safety, staffing, or compliance decisions. For organisations, portfolio screening and pilot API access package the same data in a report or integration workflow. See that page for the same limitations restated.