Summer Heat Puts 2026 World Cup Teams to the Test

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BY BEN TRACY, SENIOR CLIMATE CORRESPONDENT ON ASSIGNMENT FOR CLIMATE CENTRAL

As the 2026 World Cup kicks off across North America, the toughest opponent may not be on the field. It could be the heat.

From Mexico City to Miami, several tournament host cities may face sweltering summer conditions that experts warn could threaten player performance and fan safety. 

“It has the potential to be some of the most extreme environmental conditions for soccer in the history of America,” said Doug Casa, CEO of the Korey Stringer Institute at the University of Connecticut.

Casa says Miami concerns him more than any other host city.

“It could easily be a 100-degree day and 80% humidity,” he said.

Climate Change Raises the Stakes 

Climate Central analyzed temperature trends at all 16 World Cup host sites and found that climate change has increased the number of extremely hot summer days in 14 of the 16 host cities. The area around Miami’s Hard Rock Stadium, where matches will be played outdoors, now experiences roughly two additional weeks of extreme June and July heat compared to the 1970’s.

Several other host cities, including Dallas, Houston and Kansas City, also regularly experience dangerous combinations of heat and humidity during the summer months. Unlike dry heat, high humidity makes it harder for the body to cool itself through sweating, increasing the risk of dehydration, heat exhaustion and heatstroke.

Inside The Heat Lab

The Korey Stringer Institute studies how athletes, laborers and members of the military can safely perform in dangerous heat. The institute is named after former Minnesota Vikings player Korey Stringer, who died from heatstroke in 2001 during training camp.

Inside the institute’s heat labs, researchers simulate punishing conditions similar to those athletes may experience during summer tournaments. Before the 2021 Tokyo Olympics, the U.S. Women’s National Soccer Team trained there to prepare for Japan’s oppressive heat and humidity.

Researchers say heat and humidity affect far more than comfort. As body temperatures rise, athletic performance drops.

“Because if your temperature’s lower they just perform better,” Casa explained. “They can cover more distance, have more sprints, faster sprints. All of those things can happen if you’re less dehydrated and less hyperthermic.”

What Happens When the Body Overheats?

To demonstrate the impact, researchers use treadmill tests in climate-controlled rooms where they increase both the pace of the runner and the temperature.

“So right now the room is about 100 degrees,” said Rebecca Stearns, chief operating officer of the Korey Stringer Institute.

Within minutes, the subject’s body temperature climbed rapidly to 102.5 degrees. The test ends if a person’s core temperature reaches 104 degrees. Beyond that threshold, the risk of heatstroke rises sharply, potentially leading to organ failure or death.

“The outcome for heat stroke all boils down to the number of minutes that the body is above approximately 105 degrees,” Casa said. “We literally don’t know of anyone on planet Earth who has ever died from heatstroke if their temp gets under 104 within 30 minutes.”

Are Current Heat Protocols Enough?

FIFA, international soccer’s governing body, has introduced heat protocols in recent years, including mandatory cooling and hydration breaks when temperatures reach certain thresholds. Casa says it’s unlikely a player would suffer heatstroke during a World Cup match, but he believes the current hydration policy, which calls for three-minute cooling breaks during each half, may not go far enough.

“That is just absolutely not long enough to have an impact,” he said. “My suggestion would be to make that 5 or 6 minutes.”

The dangers are not limited to elite athletes. Fans packed into outdoor stadiums for hours at a time may also face heat-related illnesses, particularly in cities where temperatures can remain above 90 degrees well into the evening. Tournament organizers have added shaded fan areas, cooling stations, misting tents and expanded medical staffing at venues.

A Growing Challenge Beyond the World Cup 

Scientists say human-caused warming is increasing the frequency and intensity of extreme heat events, raising concerns about how outdoor sports tournaments will adapt in the years ahead. Dealing with extreme heat is becoming increasingly difficult for players and coaches at every level of the sport.

Marisa Abegg grew up on the soccer field and later played two seasons professionally, where she learned firsthand how brutal extreme temperatures can be.

“You just know how miserable it is to run around in hot weather,” she said. “It has such a huge impact on the way you play.”

She now coaches youth soccer in Connecticut and has already canceled practices this spring because of an early season heat wave.

“The weather is tending to be hotter on a consistent basis, even in months like April and May,” she said. “I think it’s just going to play more and more of a role going forward.”