This page turns a WBGT reading into the three things a practice plan actually needs: how long practice can run, how much of each hour is rest, and what athletes are allowed to wear.
It also handles the two adjustments that published tables assume you will make yourself, and that most programs quietly skip: equipment and acclimatization.
Practice limits by WBGT
| WBGT | Maximum length | Rest per hour | Equipment |
|---|---|---|---|
| Under 82.0°F | Normal | 9 minutes, in 3 breaks | Full equipment |
| 82.0 to 86.9°F | Normal | 12 minutes, in 3 breaks | Full equipment, close monitoring |
| 87.0 to 89.9°F | 2 hours | 16 minutes, in 4 breaks | Helmets and shoulder pads only |
| 90.0 to 92.0°F | 1 hour | 20 minutes | No protective equipment, no conditioning |
| Above 92.0°F | Cancelled outdoors | — | — |
Breaks mean shade, helmets off and fluids in hand. Standing in the sun receiving coaching is not rest, and counting it as rest is how a compliant-looking practice stops being one.
Adjustment one: equipment
Add this to the reading before you use the table above.
| Worn | Add |
|---|---|
| Shorts and shirt | 0°F |
| Helmet only | about 2°F |
| Helmet and shoulder pads | about 4°F |
| Full football pads | about 6°F |
| Marching uniform, hat and jacket | about 5°F |
| Goalkeeper kit or catcher's gear | about 3°F |
Adjustment two: acclimatization
Published thresholds describe acclimatized athletes. In the first three to five days of a season, nobody is acclimatized, and that is precisely when most exertional heat illness occurs.
There is no official numeric adjustment for this, which is a gap in most tables. The practical approach used by careful programs is to treat the first week as one category more severe than the reading indicates, and to lean on the structural protections instead: shorter sessions, equipment restrictions and no double days, regardless of what the number says.
Apply the same caution to any individual who is behind the team: transfers, late arrivals, anyone returning from illness. The team may be acclimatized; they are not.
Worked example
An 84°F reading on day three of preseason, which looks comfortable and is not.
| Athlete | Adjusted WBGT | Practice plan |
|---|---|---|
| Cross country, shorts and shirt | 84°F | Normal length, 12 minutes of rest per hour, monitor closely |
| Soccer keeper in full kit | 87°F | Two hours maximum, 16 minutes of rest per hour |
| Football lineman in pads | 90°F | Not permitted on day three regardless; acclimatization rules cap equipment at helmets and shoulder pads and prohibit full pads until day six |
Note the last row. The acclimatization schedule, not the WBGT table, is what governs there. Both apply, and the more restrictive one wins.
Running the calculation on the day
- Take the reading at the practice surface about 15 minutes before activity.
- Add the equipment adjustment for the most exposed group on the field.
- If you are inside the acclimatization window, step one category more conservative.
- Cross-check the acclimatization schedule for equipment and session limits, and take whichever rule is stricter.
- Announce the plan, set a break timer, and log the reading with the time.
- Recheck every 30 minutes and adjust if the number has moved.
What actually prevents heat illness
The reading tells you the environment is dangerous. These are the things that change the outcome once you know.
Unrestricted fluid access
Water available at all times, not only at scheduled breaks. Withholding water as discipline has killed athletes.
Cold-water immersion on site
A tub, water and ice, ready before practice starts from roughly 80°F WBGT. Cooling first, transport second, is what survives heat stroke.
Breaks that are real
In shade, with helmets off and fluids in hand. A break spent standing in the sun listening to coaching is not a break.
A culture of speaking up
Athletes hide symptoms when toughness is the measure. The program has to make reporting normal and costless.
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.
The reading, continuously
The app gives you live WBGT and an hourly forecast, so the 30 minute recheck is a glance rather than a trip to the instrument, and next week's schedule can be built around the forecast rather than reacted to.
- Real-time WBGT for your location or any city
- Hourly and 14-day WBGT forecasts to plan ahead
- Color-coded flag levels with mode-specific guidance
- Humidity, wind, sun and cloud cover behind every reading
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
How do you calculate practice modifications from WBGT?
Take the WBGT reading, add an equipment adjustment for what athletes will wear, then look the adjusted value up in your activity guidelines to get maximum practice length, required rest minutes per hour and permitted equipment.
What is a good work to rest ratio in the heat?
It tightens as WBGT rises. Common athletic guidance runs from about nine minutes of rest per hour below 82°F to twenty minutes per hour between 90 and 92°F, with practice capped at one hour at the top of that range.
Does the calculator account for acclimatization?
Published tables assume acclimatized athletes, so you have to apply this yourself. During the first three to five days, treat the reading as one category more severe and follow the acclimatization schedule's equipment and session limits, which are stricter.
What counts as a break?
Shade, helmets and equipment off, and unrestricted fluids. Time spent standing in the sun receiving instruction does not count, even though it is often recorded as a break.
Should I plan practice around the average athlete or the most exposed?
The most exposed. Set the plan by the group carrying the most equipment and the athletes who are least acclimatized, because they are the ones the thresholds exist to protect.
Related WBGT guides
Know the real heat number
Real-time WBGT, flag levels and forecasts. Free on iPhone.
