Pickleball in the heat: heat index, stop-play thresholds and safety

Not medical advice. This page summarizes guidance from the National Weather Service (NWS), the CDC, sports-medicine researchers and published play policies. If someone may have heat stroke, call 911.

Two questions come up on every hot court: when is it too hot to play, and what does heat illness look like? USA Pickleball's 2026 rulebook sets no heat limit, so players, open-play organizers and tournament directors decide for themselves. This page collects the published figures they can work from.

The heat index bands

The heat index is the NWS's measure of "how hot it really feels" when humidity is combined with air temperature. At 96 °F and 65% relative humidity it is 121 °F. The values are calculated for shade and light wind; the NWS says full sun can raise them by up to 15 °F.

Where sources differ: the table follows the current NWS chart as given by the NWS office in Amarillo. The heat index page of the NWS office in La Crosse still lists older bands, 90–105, 105–130 and 130 or higher, framed for people in higher-risk groups. The same La Crosse page gives a summer dew-point guide: 55 °F or lower is "dry and comfortable," 55–65 becomes "sticky," and 65 or higher is "oppressive."

The Upper Midwest reaches these levels too. During a late-June 2025 event, NWS La Crosse described heat indices of 100 to 105, highs in the low to mid 90s and overnight lows that "will only stay in the mid 70s to near 80," with heat advisories and warnings in effect. Since March 2025 the NWS has called its top heat products Extreme Heat Watches and Warnings; they were Excessive Heat Watches and Warnings before.

1. NWS heat index categories: caution 80–90 °F, extreme caution 90–103 °F, danger 103–124 °F, extreme danger 125 °F and up (white: below 80).
2. Pickleball Canada: heat is "generally" considered extreme from a heat index of 93.2 °F (34.0 °C).
3. Pickleball Canada: all play suspended from 104.2 °F (40.1 °C).
4. Lawrence, Kan., parks policy: all outdoor programs canceled above 115.
5. Heat indices of 100 to 105 reported by NWS La Crosse in late June 2025.
6. Full sun can add up to 15 °F to a shade reading (arrow: 90 in shade, up to 105 in sun).

HeatRisk and WBGT: two other measures

HeatRisk is an experimental NWS product that gives each location a daily value up to seven days ahead. It weighs how far temperatures sit above normal, the time of year, whether nights bring relief and CDC heat-health thresholds. The CDC's guide to it (reviewed September 18, 2025):

Wet bulb globe temperature (WBGT) adds sun and wind to temperature and humidity. The Korey Stringer Institute at the University of Connecticut gives it as 0.7 × wet-bulb + 0.2 × globe + 0.1 × dry-air temperature, and the NWS calls it especially useful for athletes. Thresholds are not one-size-fits-all: a 2018 Journal of Athletic Training study of 61 football heat-stroke deaths proposed stopping training at a WBGT of 29.0 °C in Region 1 (which takes in the northern tier of the US), 31.0 °C in Region 2 and 32.3 °C in Region 3, because acclimatization depends on the weather athletes usually train in.

Published thresholds for pausing or stopping play

The Canadian suspension point (104.2 °F) sits just inside the NWS danger band; Lawrence keeps youth programs running, shortened, up to 115.

Why the court can be hotter than the forecast

• Arizona State University researchers measured five Phoenix-area venues, including asphalt tennis courts, in June and August and compared them with weather stations: on-site readings averaged about 83 °F against 78 °F at the stations. The lead researcher noted that weather apps draw on such stations.
• A 2022 study at Doshisha University in Japan (Scientific Reports, 2024) logged hourly WBGT on a blue hard court from June to September. Its median was 28.9 °C against 28.2 °C estimated from a weather station 3.8 km away, and 32.5 against 31.7 in the hours the station rated “danger.” On hot days the court ran significantly hotter at 9 and 10 a.m., noon and 1 p.m.; by 5 p.m. the station estimate was the higher one. The authors suggest measuring on site and moving matches to early morning, evening or night.

Heat illness: signs and first steps (CDC)

In a sanctioned match

A player who needs care can ask for one medical time-out per match, including between games (21.C, 21.C.3). Once medical help arrives the referee starts a 15-minute clock; a player who cannot continue after it retires from the match (21.C.6–21.C.9). Under the referee time-out rule, water or other fluids on the court must be cleaned up (21.D.3), and a game suspended for extenuating circumstances resumes with the same server, score and remaining time-outs (21.H). Details are on the time-outs page.

Hot-day checklist

• Check the heat index and HeatRisk for the court's location, not only a phone app, and add for full sun.
• Play in the morning or evening rather than around midday (Baptist Health; Doshisha study).
• Build up over the first hot days: shorter or easier sessions (Baptist Health). Acclimatization takes 7 to 14 days and brings earlier, heavier sweating and a lower heart rate (Korey Stringer Institute).
• Drink "a few tall glasses of water a couple of hours before you play," sip during pauses and drink afterward; low-sugar sports drinks can replace salts (Baptist Health).
• Light-colored, loose clothing, a hat and sunscreen; pause as often as needed (Baptist Health).
• Chronic conditions and some medicines lower heat tolerance: ask a clinician first (Baptist Health). More on older players is on the seniors page.
• Know the CDC signs above, and who on site will call 911.

Emergency-department studies of pickleball injuries, including heat and heart events, are compared on the injuries page. For the other end of the year, see winter pickleball in the Upper Midwest.