Mississippi schools no longer have the option of managing heat by thermometer. The MHSAA now mandates wet bulb globe temperature readings to determine whether an outdoor practice can be held, how long it can run, and what equipment athletes can wear.
For athletic trainers and coaches heading into fall camp, that shifts the question from is it hot out to something more operational: who is taking the reading, how often, how the number reaches the coach on the field, and what happens when conditions cross a threshold mid-practice.
MHSSA WBGT Policy for High School Athletics
To help schools understand what the policy requires and how to put it into practice, Perry Weather brought together William Carey University’s Jessica Tullos, MS, ATC, LAT and Perry Weather Director of Science David Martin, PhD. They discussed the research behind the move to WBGT, what monitoring actually looks like when one athletic trainer is covering several fields, and how Mississippi schools can protect athletes without surrendering more practice time than conditions require.
What Mississippi Schools Need to Know
MHSAA activity modifications are tied directly to the WBGT reading at the practice site. The specific modifications can be found below.
A few operational notes that came up repeatedly during the discussion:
- The mandate applies to outdoor practices and workouts, including summer conditioning — not to competitions
- Readings should be site-specific, with priority given to the equipment-laden sport
- Conditions must be monitored throughout practice, not read once at the start
- If WBGT rises during practice, the corresponding break requirements take effect immediately
- Schools should keep their WBGT readings on file as documentation
What to do in each Wet Bulb Globe Temperature Zone
Conditions can move from one zone to another while athletes are already on the field. Schools therefore need a process for continuing to monitor WBGT, recognizing when a threshold has been crossed, and getting the corresponding instruction to coaches quickly enough for practice to actually change.
“You can have a tub on site, and if you don’t know where it is and it’s covered in cobwebs during practice, it’s not helpful at all in a heat emergency.”
– Jessica Tullos, MS, ATC, LAT, William Carrey University
Mississippi State Weather Policies for MHSAA Schools
Read about the updated guidelines, and how it affects your school.
Why the MHSAA Chose Wet Bulb Globe Temperature
Most athletic programs recognize heat index. But heat index was built for a person walking in the shade in ordinary clothing, not football two-a-days, marching band, or soccer conditioning in direct sun.
How WBGT Works
WBGT is a better measure because it combines air temperature, humidity, wind and heat from the sun. Humidity matters most in Mississippi. The measurement works by tracking how quickly water evaporates from a damp surface, which mimics how an athlete’s sweat cools the body. When the air is humid, sweat evaporates slowly, so the body has a harder time cooling down.
“It really gives us a great idea of the human body’s ability to evacuate heat in that environment.”
– Dr. David Martin, Director of Science, Perry Weather
How WBGT is Different than Ambient Temperature
That difference is why a WBGT number and an air temperature number should never be read on the same mental scale. Martin had just returned from two weeks of heat research at White Sands Missile Range in New Mexico, where ambient temperature hit 106°F at roughly 30% humidity — and WBGT was only just breaking 90.
“There’s this disconnect where people think that 90 [WBGT] is somewhat related to 90 ambient temperature. The scales are completely different.”
– Dr. David Martin, Director of Science, Perry Weather
In Mississippi, the relationship runs the other direction. Ambient temperatures in the mid-to-high 90s paired with Gulf humidity can push WBGT past 90 and into the most restrictive practice zones — conditions that are meaningfully more dangerous than a 106°F desert afternoon.
“If you just went by ambient temperature, we would miss a lot of things — with how low our ambient temperature can be here in Mississippi, but with the humidity corresponding with it.”
– Jessica Tullos, MS, ATC, LAT, William Carrey University
The Impact of Wet Bulb Globe Temperature & Activity Modifications
The case for WBGT-based activity modification is well documented. Analysis of exertional heat stroke fatalities in youth, high school, and collegiate football found that 100% occurred during conditioning sessions, 97% involved linemen, and 37% involved exercise being used as punishment. No fatalities occurred during game play.
Separately, at the University of Georgia, Dr. Andrew Grundstein mapped fatal exertional heat stroke cases against the WBGT conditions present at each incident. That research helped shape Georgia’s WBGT-based activity guidelines. After implementation, exertional heat illness rates fell 30% to 100% across heat-risk categories — the result that helped start the wave of state adoptions Mississippi is now part of.
Monitoring WBGT With An On-Site Perry Weather Station
The MHSAA permits app-based WBGT readings, and the panel was direct about the fact that something is better than nothing. The broader consideration is whether the process around the reading can support day-to-day operations.
A workable system needs to measure conditions on-site, keep monitoring as they change, alert the right people, connect the threshold to the required action, and create a record without adding another manual task to someone’s day.
Automatic WBGT Readings with Perry Weather
A Perry Weather station measures WBGT continuously at the school rather than relying on a regional estimate or requiring someone to retrieve each reading by hand. A black globe sensor plus dedicated humidity, wind speed, and solar radiance sensors capture all four WBGT inputs on site. When conditions cross a configured threshold, athletic trainers, coaches, and administrators receive the same alert at the same time, and the reading is timestamped and logged automatically.
Automating WBGT Communication Across Staff
A WBGT reading only supports a safer practice when it reaches the people making adjustments. With a handheld device, someone has to check the reading, determine the applicable zone, and communicate the change to each coach.
That process gets difficult when several teams, fields, or campuses are active at once.
Jessica described exactly that constraint at William Carey, where two athletic trainers were covering five or six simultaneous practices and games. Coaches were given the app, and the school’s protocols — set slightly more conservatively than the state minimum in a few places — were loaded into the platform.
“They don’t have to be out there chasing down the coach or checking. The weather station’s checking that for us, and it’s notifying them.”
– Jessica Tullos, MS, ATC, LAT, William Carrey University
That matters because heat is not the only emergency on the field. Cardiac events, orthopedic injuries, and concussions all compete for the same athletic trainer’s attention — and, as Jessica put it, athletic trainers are typically not the certified weather person on campus, they’re the default weather person.
“Something is better than nothing, but we want to really give you guys the best. The whole goal is to make it almost impossible for a coach who’s busy running practice to miss the change.”
– Eric Wingfield, Mississippi Account Executive, Perry Weather
How Perry Weather Helps Beyond Heat
Beyond heat, Perry Weather supports schools across Mississippi and the Southeast on the full range of weather decisions affecting outdoor athletics — lightning detection, wind, and severe weather alerting on the same platform. Forecasts help staff build alternate plans ahead of practice, while the on-site reading remains the source of truth once activity begins. Schools can also reach Perry Weather meteorologists directly when a call on a tournament or a game time is harder to make.
“You can have every technology in the world, but if you can’t interpret it — or explain why it’s happening to your athletes and your coaches — it doesn’t help them.”
– Jessica Tullos, MS, ATC, LAT, William Carrey University
