Where extreme heat could threaten the World Cup, endangering players and fans

The upcoming FIFA World Cup is expected to be the most-watched sporting event in history, with more than 5 million people slated to attend an expanded competition hosted across the United States, Canada and Mexico.

But with 104 matches scheduled for the height of North American summer, scientists warn the tournament could also be one of history’s hottest.

Rising global temperatures have dramatically increased the risk of dangerous heat and humidity during this year’s World Cup games, according to a new analysis from the climate research group World Weather Attribution - making conditions during the event less safe for players and spectators alike.

The analysis found that roughly a quarter of the scheduled matches this year are likely to be played amid heat and humidity levels that make it harder for the body to stay cool. Using state-of-the-art climate models, the researchers evaluated the chance the weather in each host city would exceed temperature thresholds set by the global soccer player’s union, FIFPRO, at the time of a match.

Though a handful of stadiums have retractable roofs that allow for temperature control during matches, several high-risk host cities - including Miami, Philadelphia and Kansas City, Missouri - have stadiums that cannot be air-conditioned, the analysis found. The World Cup Final, scheduled for July 19 at the open-air MetLife Stadium in New Jersey, has a 1-in-37 chance of happening during heat so severe that player’s union guidelines say matches should be postponed.

Chicago is not hosting any World Cup games.

“That … one of the biggest sporting occasions on the planet faces a non-insignificant risk of being played in ‘cancellation-level’ heat should be a wake-up call for FIFA and fans,” said Friederike Otto, a climate scientist at Imperial College London and co-founder of WWA. “There is no aspect of society not affected by climate change.”

The analysis, which uses peer-reviewed methods but was not published in an academic journal, underscores the growing climate threat to sports, the authors said. This year, play at the Australian Open was suspended when the temperature shot up past 100 degrees Fahrenheit. In 2024, a referee collapsed from dehydration during a sweltering Copa America match in Kansas City.

A 2017 study in the journal Current Sports Medicine Reports found that exertional heat stroke, caused by intense physical activity amid hot conditions, was one of the top three causes of sudden death among athletes.

To determine whether conditions this summer posed a threat to World Cup players, the WWA analysis focused on a metric known as “wet bulb globe temperature” (WBGT), which takes into account the effects of wind, sunlight and humidity as well as air temperature. Since these factors can affect the body’s ability to cool itself, scientists say WBGT is a better measure of when heat becomes dangerous.

At a WBGT of 26 Celsius - equal to about 85 degrees Fahrenheit on a day with 50% humidity and a gentle breeze - athletes are at risk of heat strain and must take frequent cooling breaks, according to FIFPRO. The WWA analysis estimates that 26 matches are likely to be held in these conditions.

At a WBGT of 28 Celsius, sweat doesn’t evaporate as well, and people’s core temperature can begin to rise beyond safe levels. This is the point when FIFPRO says matches should be canceled.

FIFA, the governing body that oversees the World Cup, sets a higher threshold for canceling play, at a WBGT of 32 Celsius.

In an emailed statement, a FIFA spokesperson said that the association has a heat illness task force and a dedicated meteorology team to help make weather-related decisions. When high temperatures are in the forecast, fans will be allowed to bring water bottles into venues, and stadiums will deploy measures such as misting systems, cooling buses and expanded water distribution.

“FIFA will continue to monitor conditions in real time … and stands ready to apply established contingency protocols should extreme weather events occur,” the statement said.

Representatives from FIFPRO did not immediately respond to a request for comment.

FIFA announced late last year that players during the 2026 World Cup would have three-minute “hydration breaks” during each half of games, regardless of the temperature. Teams will have a minimum of three rest days between matches, and substitutes and support staff will be able to sit at climate-controlled benches, according to a FIFA spokesperson. Match doctors have also been trained to use specialized “cooling bags” to help treat anyone who suffers from heat illness.

But more is needed to keep people safe, said physician Chris Mullington, a contributor to the WWA analysis. At least five games are expected to occur amid WBGT conditions of 28 Celsius or above - a doubling since 1994, when the World Cup was last held in North America. Though several of these matches will be in air-conditioned venues, the heat poses a risk to outdoor festivals where fans are expected to gather before, during and after games.

Though they will not be as physically active as the players on the field, these crowds are likely to include children, elderly people and those with health conditions that make them more vulnerable to heat, Mullington said. They are less likely to be physically acclimated to extreme temperatures and won’t have access to the same specialized medical care if they fall ill.

“When WBGT thresholds are exceeded, the response should be a whole-event planning, not just a pitch-sized planning,” he said.

Wednesday’s analysis is just the latest warning about heat risks during the highly anticipated event. Last year, a group of researchers from Britain and Canada reported that 14 out of 16 host locations are likely to exceed a WBGT of 28 Celsius in an average year.

That study’s lead author, Donal Mullan, a senior lecturer in physical geography at Queen’s University Belfast, said that in addition to the tangible threats that extreme heat poses to the safety of players and even to fans, it also can lead to sluggish games where the pace slows down and athletic performance declines.

“It’s not what the fans want to see,” he said.

Mullan said FIFA deserves credit for shifting kickoff times for many World Cup games later in the day, even if it means extremely late TV viewing times for fans in places such as Europe, Africa and the Middle East. But even a later kickoff, such as the 5 p.m. start to the runner-up game in Miami, could still turn out brutally hot - especially if a prolonged heat dome settles over the region.

Regardless of this summer’s specific conditions, Mullan said, “there’s no getting away” from the fact that as the world gets hotter and hotter, extreme heat will be a factor for the World Cup going forward. The next two tournaments are scheduled to be hosted by Morocco, Portugal and Spain in 2030 and Saudi Arabia in 2034.

Ben Noll contributed to this report.