Wet-bulb globe temperature

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:

${\displaystyle \mathrm{W}\mathrm{B}\mathrm{G}\mathrm{T}=0.7T_{\mathrm{w}}+0.2T_{\mathrm{g}}+0.1T_{\mathrm{d}}}$

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:

${\displaystyle \mathrm{W}\mathrm{B}\mathrm{G}\mathrm{T}=0.7T_{\mathrm{w}}+0.3T_{\mathrm{g}}}$

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.

Uses

The American Conference of Governmental Industrial Hygienists publishes threshold limit values (TLVs) that have been adopted by many governments for use in the workplace. The process for determining the WBGT is also described in ISO 7243, Hot Environments - Estimation of the Heat Stress on Working Man, Based on the WBGT Index. The American College of Sports Medicine bases its guidelines on the intensity of sport practices based on WBGT.

In hot areas, some US military installations display a flag to indicate the heat category based on the WBGT. The military publishes guidelines for water intake and physical activity level for acclimated and unacclimated individuals in different uniforms based on the heat category. The University of Georgia adapted these categories for use in college sports as a guideline for how strenuous practices can be.