Wet Bulb Globe Temperature (WBGT) is a measurement of heat stress that takes into account air temperature, relative humidity, wind speed, and solar radiation. WBGT is a function of Wet Bulb Temperature, Air Temperature, and Black Globe Temperature. In the 1950s, the US Military started measuring WBGT to help determine heat stress on recruits during training. A flag system was then created to easily alert people of potential hazardous conditions. Today's categories differ per region, but in North Carolina, we will use the levels determine by the National Weather Service and the North Carolina High School Athletic Association. In 2018, the NC ECONet started installing black globe thermometers at its stations to more accurately calcuate WBGT.
WBGT values from the ECONet were used to assist researchers at the North Carolina Institute for Climate Studies and the National Centers for Environmental Information (NCEI) to validate WBGT values nationally through the US Climate Reference Network (USCRN). You can read more about that study here.
WBGT Category |
Effects |
Actions |
Low | | |
Elevated | Working or exercising in direct sunlight will stress your body after 45 minutes | Take at least 15 minutes of breaks each hour if working or exercising in direct sunlight |
Moderate | Working or exercising in direct sunlight will stress your body after 30 minutes | Take at least 30 minutes of breaks each hour if working or exercising in direct sunlight |
High | Working or exercising in direct sunlight will stress your body after 20 minutes | Take at least 40 minutes of breaks each hour if working or exercising in direct sunlight |
Extreme | Working or exercising in direct sunlight will stress your body after 15 minutes | Take at least 45 minutes of breaks each hour if working or exercising in direct sunlight |