Heat stress and WBGT in Singapore

What WBGT measures

Wet-bulb globe temperature is not the same as the air temperature on a forecast. It combines dry-bulb temperature, humidity (wet bulb), radiant heat from the sun (globe) and wind. That is why a still, humid 31°C afternoon in May can outrank a breezy 33°C afternoon in February.

How to use it

• Low to moderate: normal work and sport with water breaks.
• High: shorten hard efforts, add shade breaks, watch for heat exhaustion (dizziness, nausea, heavy fatigue).
• Very high / extreme: move PE, route marches and roof work into early morning. Stop if someone stops sweating or becomes confused. That is a medical emergency.

May is the hottest month on the 24-hour mean (28.6°C at Changi for 1991-2020). Combined with light inter-monsoon winds, late April through early June is the hardest stretch for outdoor labour and school sport.

Heat is not UV

You can have Extreme UV at 11am with only moderate heat stress if a breeze is up. You can have dangerous heat stress at 5pm with falling UV. Check both pages before a long session.

Questions