A chart only works if it is where the decision gets made. On a wall in the training room, inside the equipment trailer, on a clipboard at the field. This is that chart, on one page, free, with nothing to fill in first.
One page · US Letter · about 50 KB · prints clearly in colour or greyscale
What is on it
- All five flag conditions — white, green, yellow, red and black — with ranges in both Fahrenheit and Celsius, so nobody has to convert.
- The action each level requires, written as an instruction rather than a description.
- The six warning signs of heat illness, in the words someone would actually use to report them.
- The exertional heat stroke protocol: cool first, then transport, with the cold-water immersion threshold.
- A reminder that your state association sets its own thresholds, and where to check them.
Where to put it
The training room wall
Where modifications get decided, and where a substitute coach can find it without asking.
Inside the equipment trailer
The reading happens at the field, not the office. The chart should be at the field too.
The band lot
Marching rehearsal is frequently left out of athletic heat policy. Giving band its own copy fixes part of that.
Front office and nurse's station
The people fielding calls from parents need the same numbers as the people on the field.
Before you rely on it
These are the widely adopted baseline categories derived from U.S. military heat category guidance and NATA activity guidelines. Your governing body's thresholds take precedence, and several differ.
North Carolina suspends practice at 90°F where most states run to 92°F. Texas and Oklahoma set thresholds by region. Occupational limits under ACGIH are considerably lower than athletic ones. If a published policy governs your activity, print that alongside this and follow it where they disagree — see state WBGT rules.
The chart is free to print and share, including for your whole district or company. No attribution required, though a link is appreciated if you post it online.
The reading the chart needs
A chart turns a number into a decision, and you still need the number. The free WBGT app gives you a live reading for your field or site, plus hourly and 14-day forecasts so a session can be moved before anyone travels to it.
- 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
- Pro: turf surface mode for synthetic fields
- Pro: overhead cloud adjustment from what you can see
- 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.
Sources
- Casa DJ, DeMartini JK, Bergeron MF, et al. National Athletic Trainers’ Association Position Statement: Exertional Heat Illnesses. J Athl Train. 2015;50(9):986–1000. doi:10.4085/1062-6050-50.9.07
- U.S. Department of the Army. TB MED 507: Heat Stress Control and Heat Casualty Management. Technical Bulletin, Medical. April 2022.
- National Institute for Occupational Safety and Health. Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments. DHHS (NIOSH) Publication No. 2016-106, February 2016.
Common questions
Is the WBGT chart PDF free?
Yes, free to download, print and share, including across a district or company. No sign-up and no attribution required.
Does the chart show Celsius as well as Fahrenheit?
Yes, every flag condition carries both. Mixing a Celsius threshold with a Fahrenheit reading is a common and dangerous error, so both appear on every row.
Can I print it in black and white?
Yes. The flag names are set in bold type and the bands are distinguishable in greyscale, so it stays readable on an office printer.
Are these thresholds the same in every state?
No. These are the widely adopted baseline. North Carolina suspends practice at 90°F rather than 92°F, Texas and Oklahoma set thresholds by region, and occupational limits are lower than athletic ones. Check your governing body.
Can I put this chart on our school or company website?
Yes. Host it or link to it as you prefer. A link back to peaklat.com is appreciated but not required.
Related WBGT guides
Know the real heat number
Real-time WBGT, flag levels and forecasts. Free on iPhone.