Wet Bulb Globe Temperature

The Wet Bulb Globe Temperature (WBGT) represents the thermal environment to which an individual is exposed and its value gives a first approximation of the heat stress on a person. The WBGT is an International Organization for Standardization (ISO) screening method to establish the presence or absence of heat stress.

Traditionally it is calculated using natural wet-bulb temperature, globe temperature and dry-bulb temperature.

Here we present a contemporary WBGT method that uses globe temperature from De Dear (1987) calculated using the mean radiant temperature and one of the WBGT approximations from the Australian Bureau of Meteorology.

Tip

For the physically based Liljegren method used operationally by KNMI, and the 0–10 heat-force scale derived from it, see Heat Force (Liljegren WBGT).

More information:

• Australian Government Bureau of Meteorology. Thermal Comfort observations — About the approximation to the WBGT used by the Bureau of Meteorology. https://www.bom.gov.au/info/thermal_stress/#approximation
• De Dear, R. Ping-pong globe thermometers for mean radiant temperatures. H and V Engineer 60(681), 10–11 (1988)
• Guo, H., Teitelbaum, E., Houchois, N., Bozlar, M., & Meggers, F. Revisiting the use of globe thermometers to estimate radiant temperature in studies of heating and ventilation. Energy Build 180, 83–94 (2018). https://doi.org/10.1016/j.enbuild.2018.08.029
• Minard, D. Prevention of heat casualties in Marine Corps recruits. Mil Med 126(4), 261–272 (1961). https://doi.org/10.1093/milmed/126.4.261
• Stull, R. Wet-bulb temperature from relative humidity and air temperature. J Appl Meteorol Climatol 50(11), 2267–2269 (2011). https://doi.org/10.1175/JAMC-D-11-0143.1

How to use

Wet Bulb Globe Temperature Simple

You need 2 m temperature in Kelvin and relative humidity as a percentage.

It returns the WBGT in Kelvin.

calculate_wbgt_simple(2m_temperature, relative_humidity_percent)

Wet Bulb Temperature

You need 2 m temperature in Kelvin and relative humidity as a percentage.

It returns the wet bulb temperature in Kelvin.

calculate_wbt(2m_temperature, relative_humidity_percent)

Globe Temperature

You need 2 m temperature and mean radiant temperature in Kelvin and 10 m wind speed in metres per second.

It returns the globe temperature in Kelvin.

calculate_bgt(2m_temperature, mean_radiant_temperature, 10m_wind_speed)

Wet Bulb Globe Temperature

You need 2 m air temperature, 2 m dew point temperature and mean radiant temperature in Kelvin and 10 m wind speed in metres per second.

It returns the WBGT in Kelvin.

calculate_wbgt(2m_temperature, mean_radiant_temperature, 10m_wind_speed, 2m_dew_point_temperature)

Interpret the output

The Wet Bulb Globe Temperature is described in terms of the heat-related risk to human health. Scales are generally tailored to the geographical area of interest. One scale that has been adopted at the global scale is:

Wet Bulb Globe Temperature (°C)	Risk
20 to 25	Low risk
25 to 31	Moderate risk
≥ 31	High risk