Wet Bulb Global Temperature & Exercise In The Heat
June 24, 2025
Summer workouts are a crucial part of athletic development, but they come with serious risks when temperatures soar. As a parent or student athlete, you've probably wondered how coaches and athletic trainers decide when it's safe to practice outside and when activities need to be modified or canceled altogether. The answer lies in understanding wet bulb global temperature, the gold standard tool that athletic professionals use to prevent heat-related illnesses.
Wet bulb global temperature represents the evolution of sports safety from "tough it out" mentalities to science-based protection. Franciscan Health athletic trainers use this technology not to limit athletes, but to ensure they can compete safely for years to come.
What is Wet Bulb Global Temperature?
Unlike the temperature you see on your weather app, wet bulb global temperature provides a comprehensive picture of heat stress conditions. According to Paul Herman, athletic trainer at Franciscan Health, wet bulb global temperature is "a data-research-driven temperature that helps us determine whether it's safe for athletes to practice outside or not."
“What this does is it measures not only the air temperature, but the humidity as well as the convection, or how much the wind and movement of the air is playing into the overall temperature,” added Joseph Richardville, MD, Franciscan Health sports medicine doctor and team physician for the Indianapolis Indians. “It's important to take all of that data in as you're planning your activities, planning how much hydration you need, how much rest you're going to need as you're planning your day.”
The key difference between wet bulb global temperature and heat index is scope. While heat index only considers temperature and humidity, wet bulb global temperature takes into account four critical environmental factors:
- Temperature – the actual air temperature
- Humidity – moisture content in the air
- Wind speed – how air movement affects cooling
- Cloud cover – solar radiation and shade conditions
Athletic trainers measure wet bulb global temperature using specialized equipment called a digital psychrometer. This equipment provides real-time readings that directly inform safety decisions for outdoor activities.
Why Wet Bulb Global Temperature Matters More Than Regular Temperature
You might step outside on an 85-degree day and think, "This feels fine for practice," but wet bulb global temperature could tell a very different story. High humidity can make that 85-degree day feel and affect your body like it's over 100 degrees. Add direct sunlight and little wind, and the risk of heat illness skyrockets.
This is why athletic trainers don't rely on basic temperature readings or even heat index alone. Wet bulb global temperature gives them the complete environmental picture needed to make informed decisions about athlete safety.
How Athletic Trainers Use Wet Bulb Global Temperature to Make Practice Decisions
Athletic programs follow specific wet bulb global temperature guidelines that dictate everything from practice duration to equipment restrictions. Here's how the system works at many Indiana schools, using Category 3 protocols as an example:
Below 82.0°F Wet Bulb Global Temperature: Normal Activity Sports practice proceeds as usual with standard hydration protocols in place.
82.1 to 86.9°F Wet Bulb Global Temperature: Heightened Awareness Athletic staff use discretion, particularly with high-risk populations. Student athletes take mandatory water breaks every 20 minutes to prevent dehydration and overheating.
87.0 to 90.0°F Wet Bulb Global Temperature: Modified Practice Significant restrictions kick in. Football players can only wear helmets and shoulder pads (no full pads), practice is limited to two hours maximum, and water breaks occur every 15 minutes for four minutes each.
90.1 to 91.9°F Wet Bulb Global Temperature: Severely Limited Activity Practice time drops to just one hour. Football players practice without any protective equipment, and athletes get 20 minutes of mandatory breaks within that single hour of activity.
92.0°F Wet Bulb Global Temperature and Above: Black Flag Conditions All outdoor practices are canceled. No exceptions.
This systematic approach has dramatically reduced heat-related emergencies in organized sports.
What This Means for Student Athletes
As a student athlete, understanding wet bulb global temperature helps you appreciate why practice might be modified or canceled on days that don't seem especially hot to you. These decisions aren't arbitrary – they're based on scientific measurements designed to keep you safe while still allowing you to train and improve.
When wet bulb global temperature restrictions are in place, use them as opportunities to focus on technique, strategy or indoor conditioning rather than viewing them as lost training time. Your long-term athletic development depends on staying healthy and avoiding heat illness while exercising.
What This Means for Parents
Parents should feel confident that when their student athlete's school uses wet bulb global temperature protocols, trained professionals are making evidence-based decisions about safety. However, you can also be informed advocates by:
- Asking your student athlete's school about their heat illness prevention protocols
- Encouraging proper hydration before, during, and after practices
- Recognizing early signs of heat illness: excessive fatigue, nausea, dizziness, or confusion
- Supporting coaches and athletic trainers when they make difficult decisions to modify or cancel practices
When summer temperatures rise and you see practice schedules change, remember that these modifications are investments in athlete safety and long-term performance. Heat illness can end careers and, in extreme cases, threaten lives. Wet bulb global temperature helps ensure that summer training builds champions rather than creating emergencies.
By understanding and respecting wet bulb global temperature protocols, student athletes, parents, and coaches work together to create an environment where athletic excellence and safety work together.
