How hot is too hot for recess?

The short answer

There is no national rule for how hot is too hot for recess. Each school, district or child care licensing body sets its own line. The written school lines read for this page limit or end recess at a heat index between 95 F and 105 F.

The lowest and firmest number comes from child care guidance. Caring for Our Children is the national health and safety standard for child care in the US. Its standard on outdoor play says weather that poses a significant health risk includes a "heat index at or above 90°F"³. That is guidance, not law. It matches the point where the National Weather Service moves from Caution to Extreme Caution².

Two answers circulate. One says recess should come in at a heat index of 95 F. The other says children can stay out until 105 F. The 95 F lines are the better supported for children at play. The NWS says heat stroke and heat exhaustion are "possible" from a heat index of 90 F with "prolonged exposure and/or physical activity"². Recess is physical activity. The 105 F lines sit where the weather service calls heat cramps or heat exhaustion "likely", so they are a stop line, not a safe one.

What the heat index means

The heat index is the number almost every cutoff uses, so it is worth getting right. The NWS defines it as "how hot it really feels when relative humidity is factored in with the actual air temperature"¹. Sweat cools the body as it dries. In humid air sweat dries slowly, so the body feels hotter².

The NWS gives one example. At 96 F with 65% relative humidity, the heat index is 121 F¹. A few limits matter for recess:

• It is a shade number. The NWS says heat index values "were devised for shady, light wind conditions"¹. Full sunshine can add up to 15 F.
• It can read below the thermometer. In dry air the heat index can be lower than the air. At 100 F and 15% humidity it is 96 F².
• It has bands. The NWS calls 80 F to 90 F Caution, 90 F to 103 F Extreme Caution, 103 F to 124 F Danger, and 125 F or higher Extreme Danger².
• It is not the slide. The heat index is about the air on the child's body. A sunny slide can be far hotter than the air, which is a burn question.

Children also cope with heat less well than adults. Caring for Our Children says they have more skin area for their body mass. They make more heat per pound when walking or running. And they sweat less, so they cannot shed heat as well³. Leander ISD in Texas adds that children are "less likely to feel thirsty" during long play¹³.

Every written cutoff, side by side

Here are the lines read for this page. The first five rows are child care guidance, rules and charts. The last five are school recess policies from districts in four states.

The school lines cluster at 95 F. Leander is the outlier at 105 F, and even it says to "strongly consider moving all activity indoors" from 100 F¹³.

The Iowa chart needs one note. Its colors do not follow the heat index number alone. A reading of 100 F or 103 F is red in four cells and yellow in two, at 94 F air with low humidity⁷. Every reading of 105 F or more is red, and every reading from 90 F to 98 F is yellow. Its text calls 90 F "beginning to feel uncomfortable", 100 F "uncomfortable and may be hazardous" and 110 F "dangerous"⁷. LiiNK, a recess program run from Texas Christian University, uses the same grid and colors⁸.

One hot morning, walked through every rule

Take a recess at 94 F air temperature with 40% relative humidity. That is an ordinary late summer day across much of the US. On the NWS chart the heat index is 97 F¹. The Iowa chart shows the same 97 F, in yellow⁷.

Now run that morning through each line:

So on one morning, two districts bring recess inside and a third tells principals to reconsider. Two send children out for shorter or lighter play. A child care center in Wisconsin may keep everyone in, while one in Washington has no line crossed. None of these outcomes is wrong under its own rule. They are different rules.

Now suppose the yard has no shade. The 97 F reading is a shade number, and full sun can add up to 15 F¹. In the sun the same morning could feel as hot as 112 F. That would be past every line in the table, Leander's 105 F included.

Why there is no national rule

No federal law covers recess at all. The state recess laws set daily minutes and grades, not temperatures. The ones that mention weather leave the call to the school. State recess laws lists every one.

Child care is closer to a rule, because states license it. Wisconsin's center rule requires "daily outdoor activities except during inclement weather" for centers open more than 3 hours a day⁵. It then lists "temperatures above 90 degrees Fahrenheit" as inclement weather⁴. It does not mention humidity. Washington's rule lists heat over 100 F among the conditions a provider must watch and act on⁶. Most state rules compared in daycare outdoor time requirements say "weather permitting" and stop there. Caring for Our Children gives a number, but it binds no one unless a state adopts it³.

Babies and toddlers

No source read here sets a lower heat number for the youngest children. Wisconsin uses one heat line for all ages, though its cold lines differ by age⁴. The Iowa chart says infants and toddlers "are unable to tell the child care provider if they are too hot or cold"⁷. It says to protect them by limiting time outdoors and playing in shaded areas. In its red band they "should play indoors and have ample space for large motor play"⁷.

Drinks differ too. Caring for Our Children says children should have clean water at all times. But infants fed human milk get more milk on hot days, not water, "especially in the first 6 months of life"³. Childcare playgrounds covers the yard and its shade.

What to do on the hot days below the line

The cutoff is only one decision. On a hot day that is still below it, the sources agree on the rest:

Know the warning signs. Elkhart lists heavy sweating, weakness, muscle cramps, nausea, a weak pulse and clammy skin. A child with any of them gets water and moves somewhere cooler⁹. The emergency signs and what to do are in sun, UV and heat illness and first aid and emergencies. Watching for them is part of supervision, so put the plan in writing for the adults on duty.

Shade is what moves the line. Leander lists sun, partial shade or full shade as a condition to weigh¹³. A yard under a canopy keeps more days below the cutoff. Shade structures covers built shade, and shade and heat design covers where to put it. For a wider look at why heat now limits playground use, see heat, climate and playground design.

Where this answer stops

This page covers hot air on a child's body and the heat illness it can cause. It does not cover burns from hot equipment. A slide can burn a child on a day well under every cutoff here, because surfaces in sun get far hotter than the air. Heat and burn risk covers that, and the touch test belongs in daily and weekly checks.

It also does not cover sports. Wet bulb globe temperature (WBGT) is another heat measure. It counts sun and wind as well as heat and humidity. The NWS calls it "particularly effective" for active people such as athletes, and says athletic programs in many school districts use it¹. So a practice can follow a different number than recess. Air quality is a separate call too, and Collierville lists it beside the heat index¹⁰.

No source read here tested children against a given heat index, and none sets a safe time outside at each reading. A child with asthma, diabetes, epilepsy or another condition may need a lower line. Elkhart and Collierville both name these conditions⁹¹⁰. Leander asks schools to honor parent requests backed by a doctor's note¹³.

The district rules here are examples, not a survey. Policies change, so check your own school's current text. For winter, see how cold is too cold for recess. For why time outside is worth protecting in summer too, see how much outdoor play children need.