Heat safety

When is a hot room dangerous?

Short answer

There is no single indoor number that diagnoses danger. Risk depends on heat, humidity, duration, health, activity and whether cooling is available.

What to do

  • ✓Watch the people in the room, not only the thermometer.
  • ✓Move higher-risk people to a cooler place early.
  • ✓Act on heat-illness symptoms.
  • ✓Follow local heat-health alerts.

Why it works

This advice follows UK Health Security Agency guidance and the underlying principles of heat risk and vulnerability.

Important exceptions

This page cannot diagnose anyone. Follow the linked health guidance and seek urgent help for emergency symptoms.

Sources & evidence

Reviewed 2026-08-21

  1. 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