MSHSAA Recommended Use of Wet Bulb Globe Thermometer (WBGT) for Heat and Humidity Monitoring during Activity


The MSHSAA Board of Directors approved the Wet Bulb Globe Thermometer (WBGT) as the recommended measurement practice and device for measuring acceptable heat/humidity levels for practices and contests. The use of WBGT is recommended throughout the calendar year when ambient temperature is above 80 degrees. Member schools can secure and use the instruments found on the suggested list of WBGT’s located on the Sports Medicine page at




UNDER 82.0

Normal activities – Provide at least three separate rest breaks each hour of minimum duration of 3 minutes each during workout.

82.0 – 86.9

Use discretion for intense or prolonged exercise; watch at-risk players carefully; Provide at least three separate rest breaks each hour for a minimum of 4 minutes in duration for each.

87.0 – 89.9

Maximum length of participation within this range is 2 hours.

Football: players restricted to helmet, shoulder pads, and shorts during practice. All protective equipment must be removed for conditioning activities. Competitions will be delayed, rescheduled or cancelled.

All Sports: provide at least four separate rest breaks each hour for a minimum of 4 minutes per break.

90.0 – 92.0

Maximum length of participation within this range is 1 hour.

Football: no protective equipment may be worn. Competitions will be delayed, rescheduled or cancelled. There may be no conditioning activities.

All Sports: there must be 20 minutes of rest breaks distributed throughout the hour of participation. There may be no conditioning activities.


NO OUTDOOR PARTICIPATION. Delay practice/competitions until a cooler WBGT level is reached.


(a) Schools must follow the statewide policy for conducting practices and voluntary conditioning

workouts (including during the summer) in all sports during times of extremely high heat and/or

humidity that will be signed by each head coach at the beginning of each season. The policy shall follow modified guidelines of the American College of Sports Medicine and the National Athletic Trainers’ Association Position Statement in regard to:

(1)    The scheduling of practices at various heat/humidity levels

(2)    The ratio of workout time to time allotted for rest and hydration at various heat/humidity levels

(3)    The heat/humidity levels that will result in practice being terminated

(b) A scientifically-approved instrument that measures the Wet Bulb Globe Temperature must be

utilized at each practice when the temperature is greater than 80 degrees Fahrenheit to ensure that the written policy is being followed properly. WBGT readings should be taken every hour, beginning 30 minutes before the beginning of practice/event. It will be the individual school district’s responsibility to formulate a policy and procedure that includes the following:

(1)    Obtain site specific readings with priority for the equipment laden sport

(2)    Criteria for when to obtain WBGT readings

(3)    Practice/event modifications

(4)    Identify who will perform and record readings

(5)    Communication procedure for all appropriate personnel

(6)    Exertional Heat Illness Emergency Action Plan

(c) Practices are defined as: the period of time that a participant engages in a coach-supervised,

school-approved sport or conditioning-related activity. Practices are timed from the time the

players report to the practice or workout area until players leave that area. If a practice is

interrupted for a weather-related reason, the “clock” on that practice will stop and will begin again when the practice resumes.

(d) Conditioning activities include such things as weight training, wind-sprints, timed runs for

distance, etc., and may be a part of the practice time or included in “voluntary workouts.”

(e) A walk-through is not a part of the practice time regulation, and may last no longer than one hour.

This activity may not include conditioning activities or contact drills. No protective equipment may be worn during a walk-through, and no full-speed drills may be held.

(f) Rest breaks may not be combined with any other type of activity and players must be given

unlimited access to hydration. These breaks must be held in a “cool zone” where players are out

of direct sunlight.