Anna Fiorentino
| Freelance writer
As I drew back my racket to rip a forehand down the line, it felt like my reaction time had slipped into slow motion and my legs were turning to Jell-O. I watched the ball drop into the net. Trying to understand how my one tennis weapon had become a weakness in a matter of minutes, I glanced at the thermometer. It read 98 degrees. After blowing through five packs of electrolytes in the dry Arizona heat in June, I flew back home to cool, coastal Maine with a headache that lasted for three days.
The heat-absorbing hard-court tennis surface can soar some 30 degrees higher than the air temperature around it. Playing in these conditions without balancing your water and electrolyte intake can become, in the sport’s terms, an ill-fated double fault.
The dangers of oppressive heat were in full view at the Cincinnati Open this month, when world No. 5 player Novak Djokovic collapsed mid-match, as the heat exacerbated a chronic health condition. The incident led to criticism about scheduling matches in peak heat. In July at the Memphis Classic, Ekaterina Alexandrova was wheeled off the court due to heat-related illness. Even on the cooler clay surface at the French Open in May, when a heat dome trapped hot air over the region, Jakub Menšík keeled over at the end of a five-set win, as fans left their scorching seats to crowd under the court sprinklers.
Tennis is pushing athletes’ physiological limits in a rapidly warming world. In many ways, it’s the nature of the game—intense, quick sprints and powerful swings, followed by short changeover breaks on such a sizzling surface—that can quickly raise a player’s metabolic rate and make it very hard to cool down. For the past two decades, scientists have increasingly looked at a whole-body approach to managing heat on the court—one that goes beyond simply guzzling water. The hard-court surface, in a sense, has become a laboratory for heat stress management.
“Highly visible matches continue to show that elite athletes are not heat-proof,” says Babette Pluim, a leading expert in tennis and exercise medicine at the Amsterdam Collaboration on Health and Safety in Sports, adding that the governing bodies are responding. “Tennis is emerging as one of the first global sports to combine sport-specific physiological modeling, real-time environmental monitoring and structured rule changes to manage the limits of human heat dissipation.”
The risk of a hot tournament day—defined as over 82 degrees—has increased in all four Grand Slam tournament cities (New York, London, Paris and Melbourne, Australia) since 1970, according to a June report by the nonprofit Climate Central. For the U.S. Open in Queens, New York, which began this year on August 23, that risk has risen from 49 percent in the 1970s to 67 percent.
Greenhouse gases are warming the planet, and by extension, changing the rules of court. After seven match retirements from the October 2025 Shanghai Masters, followed by fierce disapproval, the Association of Tennis Professionals (ATP) became one of the last major tennis governing bodies to implement rules for play in extreme heat, aligning with guidelines used by the Women’s Tennis Association (WTA) and at the Grand Slams. They now allow players a ten-minute cooling break if temperatures exceed 86 degrees and suspend play above 90 degrees, measured by the Wet-Bulb Globe Temperature (WBGT), a metric for heat stress in direct sunlight linked to temperature, humidity, wind speed, cloud cover and the angle of the sun. In 2023, the U.S. Open began allowing the stadium roof to be closed in extreme heat.
Overheating in tennis is caused by a combination of factors, including prolonged exertion, direct sun exposure, limited cooling opportunities and matches of unpredictable duration that can last up to five hours.
“There is a greater appreciation of the challenges prompted by heat, and an effort to provide guidelines and adopt procedures to offset [them],” says Michael Bergeron, a clinical and scientific adviser in sport sciences and medicine and performance health for the WTA, which first implemented extreme weather rules in 1992.
On an oppressively hot day, blood vessels widen, sending warm blood toward the skin so that the heat can escape and cool you down. But when it’s dry out, an athlete may not be able to drink fast enough to replenish the fluids lost as sweat. On comes rapid dehydration, which reduces blood flow to organs, increases heart rate, weakens concentration and slows down the body. At higher altitudes, dehydration is apt to happen faster.
“Headache, nausea, dizziness and impaired coordination may develop,” explains Pluim, who is also chief medical officer of the Royal Netherlands Lawn Tennis Association and a researcher at the University of Pretoria in South Africa. Extreme cases can cause exertional heat stroke, which she says “involves neurological dysfunction—such as confusion, collapse or unconsciousness—with a very high core temperature, generally around or above 104 degrees.” If overlooked, exertional heat stroke can lead to multiple organ failure, cognitive disability or death.
Losing even a fraction of a percent of the body’s water may reduce grip strength and attention, a July study found, while broader research indicates dehydration leads to a slower reaction time and speed, poorer shot selection and impaired coordination and decision making. At this year’s French Open, Australian player Daria Kasatkina said temperatures often take a toll on an athlete’s mental game, calling loss of focus from heat a whole new battle on the court.
While scientists have shown for decades that individuals tolerate heat differently, extreme heatwaves in the 2010s brought a shift toward highly customized cooling plans in tennis. By 2019, the Australian Open introduced a personalized, evidence-based system called the Heat Stress Scale to measure and suspend play based on real-time environmental data and a player’s own health and physiological limits.
Did you know? Extreme heat at the 2014 Australian Open
