Colorado's WBGT Chart Stops Outdoor Practice at 86.2°F: Planning a Turf Field Around It

The decision: plan for 86.2°F, not for how mild August feels

Denver’s summers read as milder than Myrtle Beach or Jacksonville, so it’s easy to assume heat rules matter less here. They don’t. The Colorado High School Activities Association (CHSAA) runs its own wet bulb globe temperature (WBGT) chart, and its stop line for outdoor workouts is 86.2°F WBGT — a reading that isn’t the same as the temperature on your phone. WBGT folds in humidity, wind speed, sun angle and cloud cover along with air temperature, so a bright, dry, high-altitude August afternoon can post a higher WBGT number than the forecast suggests.

The planning decision comes before the turf order: a field built without shade, a cooling area and somewhere to move practice indoors is a field that goes idle on exactly the days it gets the most use. Build those into the plan from the first site visit, not after the first hot afternoon sends a team inside.

What CHSAA’s chart requires

CHSAA’s Sports Medicine Advisory Committee Handbook states it directly, highlighted on the page: “Colorado is a Category 1 state.” The heat-illness page is marked “Updated 3/6/2024” inside a handbook file dated 25 March 2026, and it sets five WBGT bands with their own activity limits:

• Under 76.1°F — normal activities, with at least three separate rest breaks an hour, minimum 3 minutes each.
• 76.3–81.0°F — use discretion for intense or prolonged exercise; at least three rest breaks an hour, minimum 4 minutes each.
• 81.1–84.0°F — maximum practice time 2 hours. Football is restricted to helmet, shoulder pads and shorts. If the WBGT rises into this band mid-practice, players already in football pants may keep wearing them without changing to shorts. All sports get at least four rest breaks an hour, minimum 4 minutes each.
• 84.2–86.0°F — maximum practice time 1 hour. Football wears no protective equipment and runs no conditioning activities. All sports get 20 minutes of rest distributed through the hour.
• 86.2°F and above — no outdoor workouts. Delay practice until a cooler WBGT is reached.

That last line is the one to build around. It isn’t a recommendation to cut practice short; it’s a stop, full stop, until the number drops. CHSAA also directs programs to the National Weather Service’s WBGT tool rather than a home thermometer, so the reading a coach checks and the reading that governs the field should be the same source.

CHSAA’s August 2025 SMAC alert reinforces why WBGT is the metric: it “evaluates heat stress by considering temperature, humidity, wind speed, sun angle, and cloud cover” and is “more accurate than the heat index.” A heat index reading and a WBGT reading can disagree, so a field plan built around the wrong number is a field plan built around the wrong stop line.

These numbers belong to CHSAA and can change. Get the current chart from your athletic director or CHSAA before you finalize a field schedule, and keep a copy with the site plan.

What a professional install plans for

A turf field that has to sit idle at 86.2°F still has to be usable the rest of the time, which is why the layout matters as much as the surface. On the free visit, we measure the field and check the ground, and the custom layout you approve is the place to settle these questions before turf goes down:

• Shade at the sideline. A rest-break rule only works if there’s somewhere shaded to take it. Mark shaded rest areas on the site plan, not as an afterthought once the field is built.
• A cooling area with a clear path. The lower bands call for scheduled rest and hydration breaks; the top band calls for stopping outdoors entirely. Either way, water access and a path off the field belong in the layout, sized for however many athletes use the field at once.
• An indoor fallback. Since practice has to move somewhere when the WBGT reading calls for it, a nearby indoor turf space or gym floor is worth planning alongside the outdoor field, not scrambling for after the fact.
• Where the WBGT device reads. CHSAA’s chart is only useful if the number comes from where the team actually plays. Decide, before the season, whether that’s a fixed monitoring point at the field or a handheld device checked before each session.

Our Denver-metro sports field turf page covers what goes into a field build in this market; the heat plan is one part of that layout, not a separate project.

Questions to settle before the project is final

Before turf, base and drainage get finalized, settle these with whoever runs the program:

1. Who owns the WBGT reading? A device on site, a phone app tied to the National Weather Service tool, or a person assigned to check it — decide which, and where it points.
2. What’s the current chart? CHSAA’s bands can be revised. Confirm you’re working from the current version, not a saved screenshot from a prior season.
3. Does the chart bind your program? CHSAA writes for its member schools. A park district, HOA field or private facility should confirm with its own governing body whether it’s adopting CHSAA’s numbers as policy or as a guideline.
4. Where does practice go when the field closes? Name the indoor space now, in the plan, rather than during the first 86.2°F afternoon.
5. Who signs off on the layout? Coaches, athletic trainers and facilities staff should all see the shade, cooling-area and access-path placement before the design is locked.

Turf surface heat is a related but separate question from the WBGT rule — our how hot does artificial turf get article covers surface temperatures directly, and the Florida high school field heat rules article shows how another state’s statute handles the same measurement question.

Before you order turf

• Get CHSAA’s current WBGT chart and confirm the 86.2°F stop line hasn’t changed.
• Decide where the WBGT reading will be taken, and by what device or tool.
• Mark shade and a cooling area on the site plan, not as a later addition.
• Name the indoor fallback space before the season starts.
• Confirm whether your program is a CHSAA member or adopting the chart voluntarily.

On the free visit, we measure the field, check the ground and build a custom layout you approve — shade, cooling area and access paths marked in, along with the site prep and base your soil needs. Call 303-349-2368 to schedule it.