The Wet Bulb Globe Temperature (WBGT) is a composite temperature used to estimate the effect of temperature, humidity, wind speed (wind chill), and visible and infrared radiation (usually sunlight) on humans. It is used by industrial hygienists, athletes, and the military to determine appropriate exposure levels to high temperatures. It is derived from the following formula:
Where
- Tw = Natural wet-bulb temperature (combined with dry-bulb temperature indicates humidity)
- Tg = Globe thermometer temperature (measured with a globe thermometer, also known as a black globe thermometer)
- Td = Dry-bulb temperature (actual air temperature)
- Temperatures may be in either Celsius or Fahrenheit
Indoors, or when solar radiation is negligible, the following formula is often used:
The WBGT index was developed in 1956 by the United States Marine Corps at Parris Island to reduce heat stress injuries in recruits; it has been revised several times.
Read more about Wet Bulb Globe Temperature: Uses
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—Henry David Thoreau (1817–1862)