Rob DawsonJun 21, 2026, 02:30 AM ET

The heat hits immediately. You think you know what's coming, but it's still a shock to the system. Sweat appears almost instantly. The first deep breath is like sucking in hot air that feels like it's being pumped out of a hair dryer.

This is the reality for some of the players at this summer's World Cup in North America.

In a specially built lab on the south coast of England, Precision Fuel and Hydration can recreate the conditions teams are facing at some venues during the tournament. In an attempt to understand what it's like, I ran for 30 minutes and walked uphill for another 20 -- roughly one half of a 90-plus minute football match -- in conditions designed to match those in Miami or Monterrey, Mexico.

At nowhere near the same intensity of professional footballers, there's still an overall drop in body weight of 0.64% during 50 minutes of exercise. Core body temperature rises by 1.55 degrees Celcius. From those numbers, it's estimated that physical performance capacity has dropped by 10% in less than an hour.

Face, hands and feet are still burning long after the workout has finished. Fortunately, in this instance, that's the end of it, but players at the World Cup don't have that luxury. With games every few days, the final whistle is when attention turns to recovering as quickly as possible to do it again.

Playing conditions are measured by Wet Bulb Globe Temperature (WBGT) -- a gauge of heat stress that accounts for air temperature, humidity, wind speed and solar radiation. At 28 degrees Celsius WBGT -- the conditions in the heat lab -- FIFPRO, the players' union, recommends that a game be postponed.

It's not a perfect science, but according to Precision Fuel and Hydration, modelling of the climate during this summer's World Cup suggests around a quarter of the matches will be played above 26 degrees Celsius WBGT, with some games predicted to exceed the 28 degrees Celsius WBGT mark. (The venues most likely to exceed the benchmark: the open-air stadiums in the southern U.S. and northern Mexico, including Monterrey; Miami; Kansas City, Missouri; Philadelphia; New York/New Jersey and Boston.

In May, a group of experts in fields ranging from health, climate and sports performance wrote an open letter to FIFA to warn that players would be exposed to "worrying levels of heat stress" at the tournament.

"Heat doesn't just make players uncomfortable, it changes the physiology of the game," said Dr. Lindsey Hunt, Senior Sports Scientist at Precision Fuel and Hydration.

"As core and skin temperature climb, the skin draws blood away from the working muscles through competitive demand to shed heat. In practice, that shows up as less high-intensity running, fewer repeated sprints and a slower tempo, especially late in each half."

In May, after playing for more than four hours at the French Open in temperatures that reached 95 degrees Fahrenheit, tennis player Jakub Mensik collapsed after hitting his final shot. He had to leave the court in a wheelchair.

Afterward, Mensik explained that his body "just turned off."

"It's insane to play in this weather," he said. "Insane."

It was much cooler -- around 77 degrees Fahrenheit -- when Scotland kicked off their World Cup campaign against Haiti in Boston on June 13. But even in a game that didn't start until 9 p.m. local time, the North American climate still took its toll.

Bournemouth winger Ben Gannon-Doak played well in Scotland's 1-0 win and was asked afterward whether he was frustrated at being substituted after 75 minutes. His answer was a firm "no."

"I was needing [to be] hooked," he said. "Both my calf muscles decided to leave the stadium before me. I'd cramped up a bit. I was more than happy to make way and get my backside on a chair."

Every athlete is different, but it's estimated that extreme heat can reduce physical performance by as much as 20% or 30%.

"The early signs of heat are easy to miss because they look like ordinary fatigue," Hunt said. "A player working harder for less, struggling to track runners, or making uncharacteristic errors late in a half.

"The real danger signs that warrant real concern are cognitive. Those are things like confusion, clumsiness, or a player who deteriorates quickly or stops sweating. At that point, it is no longer a performance question, it's a medical one."

The conditions in the U.S., Canada and Mexico have affected almost every aspect of preparation for the tournament. Netherlands boss Ronald Koeman even suggested that England picked a squad heavily influenced by the weather.

"You can tell how they are going to play by the choices they made for the English squad," Koeman said. "They are going to gamble on corners and throw-ins. That takes the least amount of energy in the hot conditions."

England coach Thomas Tuchel, meanwhile, has insisted that the preparations have been more scientific than changing his style of play. England did their best to acclimate during a training camp in West Palm Beach, Florida, with training sessions organized in temperatures reaching 90 degrees Fahrenheit.

"We know the individual reaction of the players to the heat, and we have cooling strategies in place," Tuchel said ahead of the World Cup.

"We've had help from [Olympic] Team GB and specialists all over the world to come up with solutions that help the players to adapt. We know exactly the amount of time we want to expose them in pre-camp, the ideal amount of time that you should train in the sun and that we also don't do too much."

England began their preparations more than a year ago, when the squad exercised in heated tents at a training camp in Spain. Staff have also used digital capsules that are swallowed by players to monitor core temperature and understand how each copes with extreme heat.

"You can't out-train the weather, but you can avoid being the team that is underprepared for it," Hunt said. "Proper heat acclimation, a sensible early arrival and adjusting to the local time zone won't produce a result, but they can stop the environment from eroding performance potential and recovery, which, in a tournament of fine margins, is an advantage worth having.

"The bigger gains usually come from removing disadvantages rather than adding superpowers: arriving already adapted, sleeping well in the right time zone and recovering properly between matches."

The short answer is yes. As far as the bookmakers are concerned, France and Spain are the favorites to win the World Cup. They have, arguably, two of the strongest squads and recent tournament success. France have reached the past two World Cup finals, and Spain are the reigning champions of Europe.

But in 22 editions of the men's World Cup since the first tournament in 1930, only two European nations have won outside of Europe -- Spain in South Africa in 2010 and Germany in Brazil in 2014. The last time the World Cup was played during a North American summer in 1994, Brazil came out on top.

Improvements in the science behind coping with extreme conditions mean the playing field should be more level than it was 32 years ago. Still, history suggests that the big European teams will have to win the battle with the weather if they want to win the World Cup.

Source: https://www.espn.com/soccer/story/_/id/49127277/how-european-teams-trying-beat-world-cup-heat