Curled up on a small white rectangle of cloth on the grass of a Paris park bench, Italian swimmer Thomas Ceccon inadvertently took the internet by storm by simply sleeping outside. The moment, posted to social media by a fellow Olympian on Monday, came a week after Ceccon failed to qualify for the men’s 200-meter backstroke final despite having just won gold in the 100-meter event.

In an interview with an Italian broadcaster, Ceccon blamed his performance gap on poor sleeping conditions in the Olympic Village, namely the heat. This week, media speculation that the uncomfortable temperatures were also to blame for his outdoor nap added to an already tumultuous brew of concerns about the impact of extreme weather on this year’s Summer Games. (The Italian Swimming Federation denied that Ceccon’s nap was related to conditions in the Olympic Village.)

In the weeks leading up to the Paris Olympics, weather forecasters and athletes feared the Games would be the hottest ever, surpassing the 2021 events in Tokyo, where high humidity and 90-degree Fahrenheit days prompted 100 athletes to seek medical treatment for heat illness; even more non-athletes followed. While it’s too early to know how this year’s Games will unfold, a devastating heat dome descended on Paris on July 29, lasting four days and sending temperatures soaring to 96 degrees Fahrenheit as the first week of the Games began.

During the scorching weather, national teams rushed to keep their athletes in peak condition, renting air conditioners for their bedrooms in the Olympic Village and providing them with ice vests. The Australian Olympic Committee even invested in state-of-the-art monitors to record ground-level temperature, radiation, humidity and wind speed, resulting in personalized recommendations to help their athletes manage heat risks. For some outdoor sports, such as tennis and soccer, new protocols for additional rest breaks were activated when temperatures exceeded predetermined safety thresholds.

Climate change is fueling an increase in extreme and deadly heat waves. Rings of Fire II, an Olympic heat report released before this year’s Games began on July 26, found that average summer temperatures in Paris have risen 3.1 degrees Celsius, or about 5.6 degrees Fahrenheit, since 1924, the last time the City of Light hosted the Games.

“Yesterday, climate change ruined the Olympics,” said climatologist Friederike Otto of World Weather Attribution, an academic project that studies the effects of climate change on meteorology, on July 31. “If the atmosphere had not been overloaded with emissions from burning fossil fuels, Paris would have been about 3 degrees Celsius cooler and much safer for sport.”

Just a few degrees can make a big difference for athletes. In warmer temperatures, the body is less able to dissipate the heat it generates, which can impact performance and health: A 2023 study of marathon and race-walking athletes found that a 2.7-degree Fahrenheit increase in core body temperature can result in up to 20 percent slower performance times. And as the body tries to cool down, it sweats and blood vessels dilate. When these mechanisms are overtaxed, they lead to dangerous health risks, including dehydration, organ failure, and heart attacks. And the longer a heat wave lasts, the deadlier the consequences become.

Extreme heat is affecting a wide range of sports. The Rings of Fire report, a collaboration between the British Association for Sustainable Sport and Australian climate activist group Frontrunners, documented stories from elite athletes in 15 sports about how extreme temperatures have affected their careers and health. In the report, British swimmer Hector Pardoe said he was “almost paralyzed” after suffering heatstroke that left him vomiting and unable to move during a competition in Budapest. For Japanese race walker Yusuke Suzuki, heatstroke was a torturous ordeal that took him two years to recover from.

Read more

Lessons from the World Cup: How a changing climate is changing sport

“Looking forward, I don’t think this will be any less of a problem,” said Mike Tipton, a human physiology researcher at the University of Portsmouth in the United Kingdom who contributed to the report. While Tipton is encouraged by the changes he sees in sports to protect athletes and fans from extreme heat — such as water breaks and cooling stations — he also cautions against losing sight of the immediate cause of climate change: humans burning fossil fuels.

The organizers of the Paris Olympics seem to agree. In the years leading up to the Games, the committee made unprecedented promises about sustainability, such as halving greenhouse gas emissions from the recent Olympics. But along with a menu that is 60 percent plant-based, the decision to reduce energy consumption by building dormitories in the Olympic Village with geothermal cooling instead of air conditioning has become a major source of complaints from athletes about the accommodations. Bernadette Szocs, a Romanian table tennis player, told The Guardian that the fans provided in the dorms were inadequate. “You feel that it is too hot in the room,” she said.

“I have a lot of respect for the comfort of athletes, but I think much more about the survival of humanity,” Paris Mayor Anne Hidalgo told a French radio station in 2023 about the decision to ditch air conditioning. But as temperature forecasts and concerns mounted, organizers eventually relented and ordered 2,500 air-conditioning units for teams willing to pay for them. Some, like the Korean swimming team, have opted to stay in hotels. Unequal access to such comfort has raised concerns about two-tier competitions.

Experts agree that air conditioning can create a competitive edge. “Being able to cool down at night is an important part of managing heat risk,” said Richard Franklin, a professor of public health and tropical medicine at James Cook University in Queensland, Australia. Franklin added that heat waves often bring higher nighttime temperatures that prevent the body from fully recovering, and that sleep deprivation and the physical demands of competition can compound the risks.

There are other ways athletes can reduce the dangers of competing in high temperatures.

“The best thing you can do is prepare your body for competition by getting your body used to the conditions,” says Madeleine Orr, an assistant professor of sport ecology at the University of Toronto and the author of a book on how global warming is changing sports. She says that every sport has unique risk factors, such as the amount of time you spend on open pavement or the length of the game. But for any athlete who wants to get their body properly synchronized for competition, exercising in the heat is crucial, she says. “It doesn’t eliminate the risk, but it pushes the boundaries of when they feel the impact. It makes a big, big difference.”

Hannah Mason, a public health lecturer at James Cook University and lead author of a 2024 paper analysing the impact of extreme heat on mass sporting events, said other factors, including the availability of shade and existing health conditions, should be considered in athletes’ heat-preparation plans. For example, Paralympic athletes often use equipment, such as wheelchairs, that can trap more heat.

Tipton, Orr and Mason all agreed that the growing dangers of climate change will eventually leave Olympic organizers with no choice but to shift the timing of the summer Games so that they take place during cooler months. The good news, Tipton said, is that teams and sports federations have begun to take the heat risk more seriously. “We’re seeing the nature of sports change in terms of the rules, regulations and cooling strategies that are allowed,” he said.

According to Mason, more top-down regulation of safety limits will be crucial to managing risk. With the high stakes and pressure of competition, she says, athletes are often unwilling to back down, even when conditions become dangerously hot.

“If it’s a few degrees too warm, they’re not going to back down,” she said. “We need policies to fall back on so that we’re not putting these decisions in the hands of athletes who have trained their whole lives for that event.”