Mississippi moved outdoor athletic practice onto a wet bulb globe temperature standard, replacing the heat index as the measure that governs whether and how practice runs. The reasoning the association gave is the standard one, and it is correct: the heat index measures shaded conditions, while WBGT factors in sunlight, humidity, wind speed and temperature together.
The implementation detail worth noting is that MHSAA pointed schools at free smartphone apps for the measurement, explicitly so that schools would not have to purchase specialised equipment. That is a different stance from South Carolina or Georgia, and it removes the usual budget objection from smaller districts.
MHSAA WBGT thresholds
The structure follows the chart used across the southeast, with the familiar band edges at 87, 90 and 92°F.
- Practice limited to two hours.
- Equipment restricted to helmets, shoulder pads and shorts.
- Outdoor practice capped at one hour.
- No pads may be worn.
- All outdoor practices must stop.
Below 87°F, practice proceeds with the rest break structure the policy sets out. Confirm the full table and break requirements against the current MHSAA document, since this policy is new and the details are still settling.
Taking and recording the reading
- The first reading is taken 30 minutes before the beginning of practice or the event.
- Readings continue every hour during the session. Note that this is a longer interval than the 30 minutes most neighbouring states require.
- Schools may use a free smartphone app for the measurement, which is the route MHSAA pointed to so that specialised equipment would not be needed.
- Because the interval is hourly, be alert to conditions moving between readings. Wind dropping in the late afternoon can shift the number several degrees inside one hour.
Where an app helps and where it does not
Mississippi's acceptance of apps makes the compliance route cheap, and it is worth being clear about the trade that comes with it.
An app computes WBGT for ambient conditions at your coordinates using a physical model on live weather data. It is accurate about the air. It does not know that your practice field is synthetic turf running 50°F above air temperature, or that the band lot is asphalt, or that the stadium bowl has cut the wind. An on-site instrument does.
The practical approach: use the app for the reading the policy asks for, and where you have a known hot surface, treat the app number as a floor rather than the whole answer. If a school can afford one device, put it on the hottest surface in regular use.
This policy accepts an app or internet-based source for the reading. MHSAA pointed schools to free smartphone apps for WBGT measurement, specifically so schools would not need to buy specialised equipment. The WBGT app computes the number with the peer-reviewed Liljegren model on live weather data. It reports ambient conditions at your coordinates, so it cannot see a hot artificial turf field the way an on-site device can; where you have a known hot surface, measure on it.
Warning signs of heat illness
Heat stress shows up before it becomes an emergency. Anyone on site should speak up immediately on any of these:
When in doubt, cool first and call for help. Collapse or confusion in the heat should be treated as possible exertional heat stroke: begin cold-water immersion immediately and call 911. Cooling comes before transport.
A free app that meets the requirement
The WBGT app computes the number with the peer-reviewed Liljegren model on live weather data, and forecasts it hourly and 14 days ahead so practices can be scheduled around the heat rather than cut short on the field.
- Live WBGT for your field or any Mississippi town
- On-demand readings for the hourly interval
- Hourly and 14-day forecasts
- Athlete mode with practice guidance
WBGT is estimated from weather data with the peer-reviewed Liljegren model. Where a policy requires on-site measurement, use the app for planning and as a cross-check alongside your instrument.
Common questions
What WBGT stops practice in Mississippi?
All outdoor practices must stop if the WBGT exceeds 92 degrees. Above 90 degrees, practice is capped at one hour with no pads, and above 87 degrees it is limited to two hours with equipment restricted to helmets, shoulder pads and shorts.
Does MHSAA allow phone apps for WBGT?
Yes. School athletics personnel may use free smartphone apps to measure wet bulb globe temperature, which the association noted removes the need for schools to purchase specialised weather equipment.
How often are WBGT readings required in Mississippi?
Readings should be taken every hour, beginning 30 minutes before the start of practice or the event. That is a longer interval than several neighbouring states, which require a reading every 30 minutes.
Why did Mississippi switch from heat index to WBGT?
Because the heat index measures shaded conditions, while WBGT factors in sunlight, relative humidity, wind speed and temperature together, which better reflects what athletes experience on an open field.
Is an app as good as a WBGT instrument?
For ambient conditions, it is accurate. What it cannot see is your specific surface: synthetic turf and asphalt run far above air temperature and radiate into everyone on them. Where you have a known hot surface, an on-site device gives the truer number.
Related WBGT guides
Know the real heat number
Real-time WBGT, flag levels and forecasts. Free on iPhone.
