How Roland Garros Uses Heat Science to Protect Players

The French Tennis Federation has set a firm rule: when heat reaches 32.2°C (90°F) on the court, play stops on outdoor surfaces at Roland Garros. This is the first time the French Open has used a hard temperature limit to keep players safe from extreme heat.

The measure relies on two on-site thermometers that measure something called wet bulb globe temperature (WBGT). This is a more useful measure than standard air temperature because it captures what heat actually feels like to an athlete. It accounts for air temperature, humidity, radiant heat from the sun, and wind. So far, no match has actually been cancelled under this new protocol.

The Heat Response System

The FFT's approach is graduated. When heat reaches 30.1°C, players in a match can request a 10-minute break before the third set (women) or fourth set (men). This gives relief without stopping play entirely.

At the maximum threshold of 32.2°C, play halts on all outdoor courts. However, the three main courts — Philippe Chatrier, Suzanne Lenglen, and Simonne Mathieu — can continue matches because they have retractable roofs and air conditioning. This means some competition can continue in controlled conditions while exposed courts close down for safety.

Why WBGT Matters More Than Simple Temperature

Most of us check the heat index on a weather app. But WBGT is different and more useful for athletes. The heat index only counts air temperature and humidity in the shade. WBGT also measures radiant heat — the warmth coming directly from the sun beating down on the court.

According to the National Weather Service, WBGT captures dry temperature, wet temperature, and radiant heat readings, plus it factors in wind speed, sun angle, and cloud cover. For outdoor sports, this matters. The sun's direct heat can make conditions far more stressful than the air temperature alone suggests.

Local monitoring on the actual court also beats using regional weather station data. Every venue has its own microclimate — wind patterns, shade patterns, reflective surfaces — that can change conditions significantly. Research from the California Interscholastic Federation shows this is why measuring heat stress at the exact location where athletes compete gives a more accurate safety picture.

How Different Tennis Courts Heat Up Differently

A recent study in Nature Scientific Reports tested WBGT readings on different tennis surfaces. Hard courts reached what the Japan Sports Association classifies as "Warning" heat levels (25–28°C). Sand-filled artificial grass hit "Severe Warning" (28–31°C). Clay courts reached "Danger" level (31°C and above) compared to surrounding air temperature.

This matters for Roland Garros because clay courts — the signature surface of the French Open — retain and radiate heat differently than other surfaces. The lighter color and dense structure of clay create distinct heat signatures that can push WBGT higher than players experience on grass or hard courts elsewhere.

However, research from Perry Weather found that across grass, artificial turf, and tennis courts at university complexes, WBGT readings were similar. This underscores that local monitoring remains critical because every venue has unique environmental factors.

A Shift Happening Across All Sports

The French Open is not alone. Organizations like the California Interscholastic Federation now use WBGT to set work-rest ratios, decide when hydration breaks happen, and adjust practice length across high school sports. The shift reflects a deeper understanding of how heat actually stresses the human body during intense effort.

For decades, coaches and officials relied only on air temperature. That approach missed the full picture of what an athlete faces — the sun's direct heat, humidity that prevents sweat from cooling the skin, and the work the body does. WBGT captures all of that.

We have seen this pattern before in sports safety. When concussion science matured, there was initial pushback against new protocols in football and hockey. But once the research became clear and liability concerns mounted, adoption spread rapidly. Heat management appears to follow the same arc now across professional and amateur sports. As outdoor competitions look at their own safety protocols, the French Open's visible, high-profile approach may encourage others — from marathon organizers to cycling event planners — to adopt similar WBGT-based systems.

The broader context here is that covered courts represent an interesting middle ground in how sports adapt to heat. Rather than moving everything indoors, Roland Garros suspends play on exposed courts while allowing competition to continue under closed roofs with air conditioning. This balances player safety with keeping matches on the traditional clay surface — a hybrid model that may become common as extreme weather events occur more often.

The French Open's approach positions the tournament as a safety leader in professional tennis, all while preserving the outdoor clay court identity that defines the event.