Wet-bulb globe temperature

The wet-bulb globe temperature (WBGT) is a measure of environmental heat as it affects humans. Unlike a simple temperature measurement, WBGT accounts for all four major environmental heat factors: air temperature, humidity, radiant heat (from sunlight or sources such as furnaces), and air movement (wind or ventilation). It is used by industrial hygienists, athletes, sporting events and the military to determine appropriate exposure levels to high temperatures.

A WBGT meter combines three sensors, a dry-bulb thermometer, a natural (static) wet-bulb thermometer, and a black globe thermometer.

For outdoor environments, the meter uses all sensor data inputs, calculating WBGT as:

${\displaystyle \mathrm {WBGT} =0.7T_{\mathrm {w} }+0.2T_{\mathrm {g} }+0.1T_{\mathrm {d} }}$

where

• T_w = Natural wet-bulb temperature (combined with dry-bulb temperature indicates humidity)
• T_g = Globe thermometer temperature (measured with a globe thermometer, also known as a black globe thermometer)
• T_d = Dry-bulb temperature (actual air temperature)
• Temperatures may be in either Celsius or Fahrenheit

Indoors the following formula is used:

${\displaystyle \mathrm {WBGT} =0.7T_{\mathrm {w} }+0.3T_{\mathrm {g} }}$

If a meter is not available, the WBGT can be calculated from current or historic weather data. A clothing adjustment may be added to the WBGT to determine the "effective WBGT", WBGT_eff.