When is it too hot for sports? Why athletic programs rely on ‘Wet Bulb Globe Temperature’
BOWLING GREEN, Ky. (WBKO) - With the high school football season underway, the summer heat is still at its peak. While most of us are familiar with the heat index—which calculates how hot it feels by combining air temperature and humidity—athletic programs and school districts rely on a much more comprehensive safety metric: the Wet Bulb Globe Temperature (WBGT).
If you have student-athletes in your family, understanding how WBGT works and the strict guidelines coaches must follow can help keep them safe during the hottest days of the year.
What is the Wet Bulb Globe Temperature (WBGT)?
Unlike the standard heat index, which is measured in the shade, the WBGT is designed to measure heat stress in direct sunlight. It evaluates four environmental factors to determine the true stress level on the human body:
- Air Temperature
- Humidity
- Sun Angle and Solar Radiation (how much direct sun is coming in)
- Wind Speed (whether a breeze is available to help cool the body down)
By combining these factors, WBGT provides a more accurate picture of how effectively an athlete’s body can cool down through sweat evaporation.
When does heat cancel play?
Athletic programs monitor WBGT closely to decide when to modify practice or when it is simply too dangerous to play. Here are the key thresholds coaches and athletic trainers watch for:
- Between 90°F and 92°F (WBGT): Water breaks are mandatory and must be taken at frequent intervals. Practice intensity must be reduced, and protective equipment (like football pads) should not be worn.
- Over 92°F (WBGT): All outdoor athletic events and practices must be called off, postponed, or rescheduled. At this level, the risk of heat-related illnesses like heat exhaustion or heat stroke is high.
School sports safety in the late summer heat
The start of the school year coincides with some of the most humid, sweltering weather of the year. Because student-athletes are often practicing twice a day or playing intense games early in the season, athletic directors and coaches keep a constant eye on WBGT readings on the field.
By prioritizing this measurement over the heat index, schools can proactively protect players from the dangerous physical toll of extreme summer heat.
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