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).^[1] 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.^[2]

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.^[2] A clothing adjustment may be added to the WBGT to determine the "effective WBGT", WBGT_eff.