Athletes at the 2024 Paris Olympics are competing against the toughest opponents in the world, the clock, the record books, and increasingly, extreme heat.

Rain soaked the opening ceremony, but it followed an extensive heat wave across France and much of Europe. According to the World Weather Attribution research group, such temperatures would not have been possible without human-induced climate change. The competitions began with more heat as temperatures reached 95 degrees at outdoor venues. Athletes complained about the lack of adequate cooling in the Olympic Village where they stay and some teams brought their own air conditioning units, undermining the host city’s goals to curb energy use with techniques like underfloor cooling.

For competitors chasing wins by seconds or even less, the high temperatures have been a frustrating confounding variable. The host city is no stranger to deadly heat. Fortunately none of the athletes have passed out at the Paris games so far. But as 2024 is shaping up to be the hottest on record, some current and former competitors are warning that the warming planet is posing more fundamental challenges to the Summer Olympics as we know them.

In a report published ahead of the Olympics by the nonprofit British Association for Sustainable Sport, athletes and researchers laid out their concerns about how climate change is undermining performance, health, and the future feasibility of their events.

“For athletes, from smaller performance-impacting issues like sleep disruption and last-minute changes to event timings, to exacerbated health impacts and heat-related stress and injury, the consequences can be varied and wide-ranging,” Sebastian Coe, president of World Athletics, the international governing body for track and field sports, wrote in the report.

As “global temperatures continue to rise,” Coe said, “climate change should increasingly be viewed as an existential threat to sport.”

The good news is that the organizers of the Paris Olympics seem to have learned important lessons in managing heat from past events. The 2020 Tokyo Olympics, held in 2021, were considered at the time to be the hottest Olympics in history, with temperatures averaging almost 90 degrees Fahrenheit. Many athletes saw diminished performances, and some tennis players and archers suffered heat exhaustion and heat stroke. At least 110 athletes reported some kind of heat-related illness at the Tokyo Olympic games.

Outside of the Olympics, there have been numerous sporting tournaments and practice sessions where athletes have passed out due to extreme heat. In some cases, these temperatures have led to deaths.

Extreme heat is clearly not something athletes can or should push through, though it often can’t be easily avoided for outdoor sports. It’s forcing organizers of major events like the Olympics to take more precautions to protect athletes.

As the games draw to a close and athletes set their sights on the next competitions, including the 2028 Olympics in Los Angeles, organizers are grappling with the reality that some of the toughest outdoor endurance sports will require more drastic measures, ranging from scheduling events very early or late in the day to relocating certain competitions far away from the host city. For future Olympians, the ideal training windows are narrowing for much of the year, which could end up throttling the pipeline of new athletes entering the competition.
And if climate change continues unchecked, most major cities could end up too hot to host the Summer Olympics before the end of the century.

Why do we continue to have the Olympics during the summer?

One big reason is television and sponsorships. Though the games were conceived as a competition between amateurs, many Olympians now do this for a living. Their home sports leagues often have a lull in the summer, which clears schedules for athletes to participate in the games and clears the airwaves to show them. Changing the timing of the event to the spring or the fall means diluting viewers, and thus advertiser dollars, among soccer, baseball, and football.

That all creates financial pressure to keep these events during warm weather months — but it also makes the games more dangerous and expensive, increasing the costs for organizers to invest in cooling and preventing heat illnesses.

Summer Olympics are also a tradition, but as temperatures go up around the world, the future will look much less like the past. There will be fewer ideal sites for athletes to train for outdoor events. Olympic hopefuls will have to travel to better locations to practice or seek out expensive, specialized training facilities. It will further disadvantage those without means, and over the long term, make it harder for new athletes to pick up the sport, particularly from less-wealthy countries.

This is already playing out with the Winter Olympics as fewer cities produce reliable snow and ice, making hosting a more expensive endeavor and making it harder for athletes to train.

With the amount of money and prestige at play, the Olympic phenomenon isn’t going anywhere. But for the competitors on the field and the young people hoping to be in their shoes one day, there will be fewer places where they can realize their dreams.

There are some steps that major sporting events planners are taking to cope with the heat. One is to relocate some of the major outdoor events to cooler areas. During the Tokyo Olympics, the marathon was actually held in Sapporo, Japan, more than 600 miles north of Tokyo. The cooler weather there helped, but it broke the tradition of having the marathon finish inside the Olympic stadium, and several runners still fainted and vomited as they crossed the finish line.

Another option is to schedule competitions during cooler times of the year. There’s precedent for this. The 1964 Tokyo Olympics were actually held in October in part to avoid hot weather. During the 2019 World Athletics Championships in Qatar, the marathon started at midnight. More recently, the 2022 FIFA World Cup soccer tournament, also in Qatar, ran in November and December rather than during the country’s unbearably hot summer months.

There are also ways that athletes can protect themselves. “​​The best way to prepare for competition in the heat is to train in the heat,” according to a planning document for the Paris Olympics. That can take the form of acclimatization, where athletes practice in hot, natural environments, or acclimation, where competitors train in artificial warm environments or wear additional layers of clothing to get used to warmer temperatures. But it’s a slow process, requiring athletes to begin their heat exposures two weeks before competitions start.

During the event, organizers have to pay close attention to ambient weather conditions — in particular, wet bulb globe temperature. This is a measurement that models how well the human body can cool off by sweating, and many sport regulators consider it to be a better measure of heat risk than temperature alone or the heat index.

The International Tennis Federation, for instance, has an extreme weather protocol for the Olympics that triggers when the wet bulb globe temperature reaches crests 30 degrees Celsius or about 86 degrees Fahrenheit. It allows for a 10-minute break between tennis sets where a player can leave the court to shower, change, eat, or drink. But if temperatures continue to rise, an advisory group will meet and determine whether to suspend play.

For athletes that do end up past their limits and suffer heat stroke, there’s a protocol to help them cool off, but timing is critical. “You have a 30-minute window to get someone’s temperature under 104 from the moment of the onset to assure survivability,” said Douglas Casa, a professor of kinesiology at the University of Connecticut who helped draft the plan for the Tokyo Olympics to deal with exertional heat stroke in athletes.

Prolonged heat exposure coupled with the intense exertion of a match or race can quickly turn dangerous. Athletes can experience heat exhaustion, causing extreme fatigue, dizziness, cramps, clammy skin, and nausea. That can then progress into heat stroke, where the core body temperature rises past 104 degrees Fahrenheit, causing organs to shut down.

To aid an athlete suffering from heat stroke, the first step is to diagnose the condition, usually with a rectal temperature measurement. The plan then is to “cool first, transport second.” The gold standard for cooling someone with heat stroke is an ice bath. Only after the body temperature starts to come down do you then take the athlete to a medical facility. “You can’t give up all those minutes waiting for an ambulance on site, and then waiting for a hospital to deliver care,” said Casa, who also leads the Korey Stringer Institute, named after the Minnesota Vikings player who died from exertional heat stroke in 2001.

That means the event venues need to have emergency cooling setups ready to go. But the optimal strategy remains preventing these types of complications in the first place.

Most athletes have a personal ideal temperature range where they know they will perform their best. But part of the challenge (and some say fun) of many sports is dealing with what nature throws at you.

Some of the most temperature-sensitive competitions are long-distance outdoor races, like marathon or cycling. “We know as it gets hotter, they get slower,” said Andrew J. Grundstein, a professor of geography at the University of Georgia who served on the adverse weather advisory committee for the Tokyo Olympics.

That’s because the impacts of heat scale with time and severity. Longer exposure to high temperatures can lead to dehydration and exhaustion. Muscles work less effectively. And as humidity rises, sweat doesn’t evaporate as readily, making it more difficult for the body to cool off.

Another concern is that high temperatures also lead to more air pollution. Hot, dry weather can create the conditions for dust in the air, while high temperatures accelerate the formation of ozone, a pollutant that can impair breathing and cause heart problems.

And at major competitions, athletes aren’t the only ones that have to bear the heat. Staffers and spectators may not be pushing themselves as hard as the people on the field, but they do face the same weather conditions. There are free water refill stations at the Paris Olympics for attendees, and at some events, volunteers sprayed fans with hoses and misters.

The other vulnerable group to consider is the laborers who build stadiums and get cities ready to host major events. They’re far out of the spotlight but are working against tight deadlines, which can cause lapses in safety or push workers to stay out longer in dangerous conditions. In the months leading up to the 2022 FIFA World Cup soccer tournament in Qatar, hundreds of workers died amid scorching weather. And after the closing ceremonies, workers will have to clean up and disassemble all the infrastructure.

Though the athletes at the Olympics are some of the most privileged people in the world with the best resources at their disposal, what we learn in trying to keep them safe as they pursue the limits of human performance could help protect many more people on a warming planet.