Each fall and spring Fort Zumwalt athletes and performers face the challenges of St. Louis weather. While most weather resources express the actual temperature and the “feels like” temperature, which factors in humidity, the Missouri State High School Activities Association (MSHSAA) uses the Wet Bulb Globe Temperature across the state of Missouri.
What is Wet Bulb Globe Temperature?
Wet Bulb Globe Temperature (WBGT) is a special way to measure how hot and stressed the human body feels when exercising in the sun. It is different from the regular temperature you see on a phone app because it looks at more than just the air. It also measures:
humidity (how wet the air is)
wind speed
the angle of the sun
cloud cover
To get this number, scientists use three different thermometers: one for the air, one that acts like a sweating person to see how water evaporates, and one inside a black ball to measure the heat of the sun. Even though the numbers might seem low—like 90 degrees—a high WBGT means it is very dangerous to be active outdoors.
How do school officials monitor it?
Missouri school officials use scientifically-approved tools to measure the WBGT right on the athletic fields. They must use these devices whenever the air temperature is 80 degrees or higher. Officials are required to take a reading 30 minutes before practice starts and then continue to check the temperature every hour while students are outside. This helps them make quick decisions if the weather gets too dangerous.
Is there a standard measurement school officials use?
The Tiered Safety Framework MSHSAA uses a tiered system to keep athletes safe as the WBGT goes up. As the temperature climbs, schools must follow these rules:
Under 82.0: This is considered normal, but players must still take at least three rest breaks every hour that are at least 3 minutes long.
82.0 – 86.9: Coaches must watch "at-risk" players very carefully and increase the rest breaks to 4 minutes each.
87.0 – 89.9: Practice is limited to only two hours. Football players can only wear helmets, shoulder pads, and shorts. Games must be delayed or canceled.
90.0 – 92.0: Practice is limited to only one hour, and no protective gear (like football pads) can be worn. There are no conditioning drills allowed, and players must rest for a total of 20 minutes during that hour.
Over 92: There is no outdoor participation allowed. All practices and games must be stopped or moved until it cools down.
Fort Zumwalt School District puts the safety of students and staff first. Using MSHSAA’s WBGT system is one layer of safety for our athletes and performers during extreme heat. The graphic below summarizes this information.
Resources: MSHSAA WBGT guidance, Additional MSHSAA guidance for extreme heat, Spectrum News Article explaining the Wet Bulb Globe Temperature