Heat Illness Prevention Information: All about WBGT

Heat Stress Index: WBGT

All about WBGT (Wet Bulb Globe Temperature)

You have to do more than just stay out of the heat to prevent heat illness.

What is Wet Bulb Globe Temperature?

Wet Bulb Globe Temperature (WBGT) is an environmental index representing

temperature, humidity and radiation_*1

as major factors affecting human heat balance_*2

It has been specified as a heat illness risk on the Japanese Ministry of the Environment’s heat illness prevention website since 2006.
WBGT is calculated from dry bulb temperature, wet bulb temperature and globe temperature.

Details about WBGT observations (in Japanese).

*1 Radiation heat comes from the ground, buildings, people and other sources. Hotter bodies emit larger amounts.

*2 Wind also affects human heat balance.

WBGT is calculated from dry bulb temperature, wet bulb temperature and globe temperature.

I see, heat stress is not determined by air temperature alone!

The wet-bulb temperature is a measurement of humidity, while the black globe temperature mainly reflects the effect of radiant heat.

I wonder why the wet-bulb temperature accounts for the largest percentage?

Well, sweat doesn't evaporate well when it's humid, which makes it harder for people to cool down.This increases the risk of heat illness.

This increases the risk of heat illness.

So which WBGT criteria are more important?

Daily occurrence per million people vs. daily maximum WBGT.

Well, this figure shows that heat illness is much more common on hot days when the WBGT value is over 28.

Right. Days like this are a real risk. You have to be careful!

Find out more about WBGT.

How much do you know about WBGT?
Check out your local WBGT.

Preventing heat illness

Details about WBGT observations (in Japanese).

Heat Stress Index: WBGT: ・Current WBGT and forecast; ・WBGT Guideline; ・All about WBGT
Heat Stroke Alert: ・Heat Stroke Alert; ・About Heat Stroke Alert

Heat illness prevention/countermeasures: ・First Aid for heat illness; ・About heat illness; ・Materials

Using the content on this website: ・Terms of Use

Mobile