Throughout the summer, we’ve talked about temperatures and the heat index, but there’s another measurement that’s been used to talk more specifically about heat stress in direct sunlight.

The Wet-Bulb Globe Temperature (WBGT) was originally introduced for the safety of workers outside. OSHA and the International Organization for Standardization recognize this measurement as a standard for occupational environments.

The University Interscholastic League, or UIL, is also recommending coaches use the WBGT to protect their athletes from heat-related illnesses when exercising outdoors.

Here’s why this measurement is used to keep you safe in direct heat:

What does the WBGT measurement take into account?

According to the National Weather Service, the WBGT measures the heat stress on the body based on four parameters:

• Temperature

• Relative humidity

• Wind

• Sunlight

The measurement’s output is a number in degrees (much like the heat index) and is categorized into four danger thresholds by the U.I.L: low, moderate, high, and extreme. Here’s a chart of the risk level, WBGT, and U.I.L Guidelines.

How is it different from the heat index?

The heat index is a calculation of what it feels like to our bodies based on the humidity and the temperature in the shade (i.e., not in direct sunlight).

WBGT Forecast

To find the forecast WBGT for your area, go to this website. Change the category from “Heat Risk Experimental” to “Wet Bulb Globe Temperature” and use the time bar at the top to scroll through time.