Why it works
What wet-bulb temperature means
Short answer
Wet-bulb temperature combines heat and moisture to show how much cooling evaporation can still provide.
The simple explanation
- ✓It rises when air is hotter or more humid.
- ✓It is not the same as ordinary air temperature.
- ✓Personal risk also depends on exposure, health, activity, clothing and access to cooling.
Why it works
This advice follows UK Health Security Agency guidance and the underlying principles of wet bulb and humidity.
Important exceptions
Safety, health, weather and the design of your home can change what is appropriate. Stop if an action makes conditions worse.
Related guides
Sources & evidence
Reviewed 2026-08-21
- UK Health Security Agency: Beat the heat: keep cool at home checklist ↗
Supports: Shading, ventilation, reducing indoor heat and protecting people at higher risk.
official guidance · Accessed 2026-08-21