World Cup 2026: Could heat decide who lifts the trophy?

The World Cup 2026 has now reached the knock-out stages, in which 32 countries are still playing for a place in the next round.

Besides the players and the teams, there has been one undisputed protagonist: the heat.

Even before the tournament kicked off in Canada, Mexico and the United States, health experts and professional players warned that some of the matches were going to be played under dangerous weather conditions.

To mitigate the consequences, FIFA has introduced a mandatory hydration break across all games, regardless of temperature

Now, as the tournament reaches a new round, temperatures have become as severe as predicted, with the United States expecting a heatwave from 1 July which is set to affect much of the country.

An analysis by Climate Central, an independent group of scientists and communicators researching climate change, found that several matches have already been played and are due to be played under performance-impairing heat.

“Heat is a hidden opponent that all players are also playing against,” Tom Di Liberto, media director at Climate Central, told Euronews Health.

While heat affects teams across the board, its extent and frequency are not the same for every team.

Multiple factors, such as scheduling, location and stadium conditions, mean some national teams are more exposed than others.

Argentina’s route to the final would be the most affected by extreme temperatures. All of the country’s games, if it were to reach the last stage, would be played in conditions with more than a 50% chance that heat would impair performance.

Portugal, Spain and Brazil follow, with an average of over 66% chances of their games being affected by the heat.

In the round of 32 currently being played, the hottest matches was Ivory Coast against Norway played on Tuesday, 30 June, followed by Argentina against Cape Verde, which will take place on 4 July and England against DR Congo on 1 July.

By contrast, Switzerland-Algeria, Belgium-Senegal and Mexico-Ecuador will barely be affected.

“It's just not equal at all for how these teams perform and I'm very curious to track, as we get later on to the round of 16, the quarterfinals, the semifinals, whether that'll start adding up,” Di Liberto said.

He added that as the tournament progresses, heat stress could play a key role. “When the margins are so slim, something like that can make a difference,” Di Liberto noted.

Previous research on how high temperatures impact elite football performance established a ceiling temperature at 28°C.

Above this temperature, researchers found that heat stress impairs performance and slows down players.

“Players compensate for the elevated physiological strain with more conservative play, improving pass success by prioritizing defensive play,” said Dr Oliver Gibson, Senior Lecturer in Exercise Physiology at Brunel University of London.

He added that as the body temperature increases, the risk of heat illness rises, along with cardiovascular strain and fatigue, lethargy and lightheadedness.

These temperatures caught no one off guard. When planning such a tournament in the summer in Canada, Mexico and the US, heat is to be expected.

However, climate change is accelerating the rate at which the average temperatures are rising.

Yet only three of the host stadiums are climate controlled, noted Di Liberto, and those are the ones in Houston, Dallas and Atlanta.

Most stadiums do not have cooling systems or structures to guarantee shade on the pitch or in the stands.

For Di Liberto, it is important to consider solutions for future sports events held under similar conditions.

“This is not a problem that's going away; it’s only going to continue to happen,” he added.

According to Di Liberto, this is a broader conversation that should also be had outside of football, too, with an eye on other major sporting events.

“It's an opportunity to bring a topic into focus that you may not realize is impacting the sport that you love so very much,” he added.

Over the next few years, the Women’s World Cup in Brazil in 2027, the Olympic Games in Los Angeles in 2028 and the next men’s World Cup in Morocco, Portugal and Spain in 2030 will once again put heat in the spotlight.