Heat rules: each tour and event sets its own.

The rules side by side

WBGT stands for Wet Bulb Globe Temperature. A WBGT of 30.1°C, a Heat Stress Scale level of 4 and a Heat Index of 34.0°C are different measurements, so a threshold under one rule cannot be read across to another.

ATP: the 2026 heat rule

The ATP Board approved a heat rule on 15 December 2025, in force from the 2026 season. The ATP described it as bringing the men's tour into line with the WTA and as protecting spectators, officials, ball persons and staff as well as players.

• Trigger. When WBGT reaches 30.1°C or higher during the first two sets of a best-of-three singles match, either player may request a 10-minute cooling break after the second set. Once requested, the break applies to both players.
• During the break. Players may cool down, drink, change clothes, shower and receive coaching, supervised by ATP medical staff.
• Suspension. Play is suspended when WBGT exceeds 32.2°C.

WTA

An AP report carried in 2025 says the WTA has used a WBGT-based heat rule since 1992, allowing a longer break between sets in singles when the reading exceeds 30.1°C (86.2°F). The current WTA rule text was not found, so the exact present wording is unconfirmed; the details rest on news reports and on the ATP's statement that its rule aligns with the WTA's.

Australian Open: the Heat Stress Scale

The Australian Open announced its Heat Stress Scale on 29 December 2018 for the 2019 tournament, replacing the WBGT reading it had used before. The tournament's own policy page was not found; the details below come from news reports.

• The scale. It runs from 1 to 5 and combines air temperature, radiant heat, humidity and wind speed, with readings taken across Melbourne Park through the day (Al Jazeera, 2018).
• Level 4. Organisers can add a 10-minute break between the second and third sets of women's singles and between the third and fourth sets of men's singles. No extra break is given if an arena roof closes before the first set ends (women) or the second set ends (men) (AP, January 2026).
• Level 5. Singles play is suspended on the outside courts and the three arena roofs are closed. The tournament referee may suspend play, order extra cooling breaks, close roofs for upcoming matches and decide when play resumes, with at least 30 minutes' notice to players (AP, January 2026).
• In 2026. The heat measures were invoked on Saturday 24 January 2026, when the scale reached 5, which organisers said was the first activation since 2023, and again on Tuesday 27 January 2026, when the site peaked at just over 42°C.

A search excerpt says the scale was developed with the University of Sydney and Tennis Australia medical staff; that is unconfirmed.

US Open

The current USTA heat rule text was not found. News reports, unconfirmed against the rule itself, say the US Open brought in a men's extreme heat policy during the 2018 tournament allowing a 10-minute break between the third and fourth sets (ESPN, 2018), and in 2023 added a step under which the stadium roof is partially closed at the next set break while the heat rule is in force (AP, 5 September 2023).

Olympic and Paralympic tennis (ITF)

The ITF's own pages on these policies did not open for the research, so the following rests on search excerpts and a news agency report and is unconfirmed. Under the ITF Extreme Weather Policy used for tennis at the Paris 2024 Olympics, WBGT was measured from 11:00 local time every 30 minutes; at 30.1°C the policy took effect, allowing a 10-minute break between the second and third sets with a player's consent, and the referee could suspend play. A Spanish news agency (EFE) reported the policy activated on 30 July 2024. For wheelchair tennis at the Tokyo 2020 Paralympics, the ITF is described as using a lower threshold of 28.0°C WBGT.

Pickleball Canada

Pickleball Canada's Weather and Air Quality Safety Guidelines (posted April 2026) cover its own tournaments and events:

• Heat. Generally considered extreme when the Heat Index, air temperature combined with relative humidity, meets or exceeds 34.0°C (93.2°F). All play is suspended at 40.1°C (104.2°F) or above. The tournament director may declare extreme conditions at a lower reading.
• Other extreme weather. Lightning, wind, rain and weather warnings may be declared extreme before or during matches on all courts; officials then tell players and play is suspended until conditions are no longer extreme.
• Air quality. The guidelines point to the Government of Canada Air Quality Health Index. Tournament directors should consider delaying or cancelling affected matches only when the index is very high (10 or more) at match start, and keep the final right to cancel if conditions are dangerous.

Bodies with no heat rule found

No heat policy was found from USA Pickleball, the PPA Tour, Major League Pickleball, the FIP or Premier Padel, World Squash or the PSA, or the BWF. That means none was found in the research, not that none exists; each organiser's own rules decide. No lightning rule was found from the USTA, the LTA, Tennis Canada or World Tennis. A search excerpt of a Tennis Australia extreme weather policy (a 2014 document under a 2018 title) says it covers lightning as well as heat, making the safety of players, officials and spectators the priority; that page could not be opened.

What researchers say about heat policies

Bandiera and colleagues (British Journal of Sports Medicine, August 2024) reviewed the heat policies of 32 international federations covering 45 Paris 2024 sports and placed 15 sports in high, very high or extreme heat-risk categories. Of those 15, one had no heat policy, three named no measurement, seven used WBGT, and the rest used water temperature, air temperature with humidity, or a heat stress index. The authors note that most of these indices were developed for soldiers or workers, not athletes. Separately, the 2025 review of high-performance tennis by Amor-Salamanca and colleagues lists hot and humid conditions among the factors it associates with injury.