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Climate Central says 97 of the 104 scheduled matches at the 2026 FIFA World Cup could face temperatures linked to reduced player performance.
Nearly half of all matches have at least a 50% likelihood of experiencing “performance-impairing heat”, according to the analysis.
US venues are expected to face the highest heat risks, with Portugal’s match in Houston and Argentina’s game in Kansas among those flagged.
Researchers say temperatures above 28°C can reduce sprint frequency, distance covered and recovery time, affecting match pace and tactics.
More than 100 current and former players have called on FIFA to strengthen heat-safety protocols ahead of the tournament.
Rising heat linked to climate change could affect player performance at the 2026 FIFA World Cup, including for senior stars such as Lionel Messi and Cristiano Ronaldo, according to a new analysis by Climate Central.
The tournament, which begins on June 11, 2026, will be played over five weeks across 16 cities in the United States, Mexico and Canada.
Climate Central, a US-based climate research organisation, analysed the likelihood of match temperatures rising above 28 degrees Celsius, a threshold that previous research has linked to reduced player performance.
It found that 97 of the 104 scheduled matches now face a higher probability of encountering such conditions. Nearly half of all matches have at least a 50 per cent likelihood of experiencing what the report calls “performance-impairing heat”.
In 26 matches, climate change has increased that likelihood by at least 10 percentage points, the analysis said. The findings raise questions about how extreme heat could shape the pace, tactics and safety of the world’s most watched football tournament.
“The World Cups of the past won’t happen again — not because the players have changed, but because the planet has,” said Shel Winkley, a meteorologist at Climate Central.
The heat risk is expected to be highest at several US venues. Portugal, who are scheduled to play in Houston, face a 96 per cent likelihood of experiencing debilitating heat, according to the analysis. Argentina face a 68 per cent chance of playing in performance-impairing heat in Kansas.
That could put additional strain on Ronaldo and Messi, two of the game’s biggest names and among its oldest elite players.
Former Indian footballer Crompton Dutta said heat tends to affect older players more sharply. “Heat, beyond a threshold value, definitely affects the performance quotient, particularly of older players,” he said. “If someone is used to performing 10 sprints in a match, now, particularly an older player, he may be able to do seven sprints in higher heat.” he added.
Other teams playing at hotter US venues, including Houston and Dallas, are also expected to face high heat risks. The report names Croatia, Curacao, DR Congo, England, Germany and Japan among teams likely to experience conditions similar to Portugal.
By contrast, Australia’s matches in Vancouver carry only a 1 per cent likelihood of such heat, the report said. Venues in Canada and Mexico are expected to be significantly cooler than many US locations.
The report said temperatures above 28°C can reduce sprint frequency, total distance covered and recovery time. That can affect not only player health, but also match tempo, tactics and the style of play.
“In football, a typical midfielder runs well over 10 kilometre for each match,” said John Toohey-Morales, an honorary member of the American Meteorological Society.
“It’s a high-intensity effort, with directional changes and short bursts of acceleration,” he said. “Climate Central’s analysis shows how these elite athletes will likely be slowed by hotter temperatures which are being boosted by climate change.”
Players and sports scientists have also warned that heat can affect the quality of the game itself.
“This analysis makes clear that rising temperatures are not only a serious health risk for players and fans, but they are also starting to affect the quality of the game itself,” said Morten Thorsby, who plays for Norway’s national team.
“When heat impacts sprinting, recovery, and overall intensity, it changes the way football is played — and not for the better,” he said.
“It’s a high-intensity effort, with directional changes and short bursts of acceleration,” he said. “Climate Central’s analysis shows how these elite athletes will likely be slowed by hotter temperatures which are being boosted by climate change.”
Players and sports scientists have also warned that heat can affect the quality of the game itself.
“This analysis makes clear that rising temperatures are not only a serious health risk for players and fans, but they are also starting to affect the quality of the game itself,” said Morten Thorsby, who plays for Norway’s national team.
“When heat impacts sprinting, recovery, and overall intensity, it changes the way football is played — and not for the better,” he said.
Thorsby said he had signed a players’ letter to FIFA calling for stronger heat-safety protocols.
More than 100 current and former players from 21 countries, backed by climate scientists, have submitted an open letter to FIFA ahead of the tournament, saying current heat-safety rules are inadequate and players face serious heat-stress risks.
Experts say heat risks become particularly serious during high-stakes matches, when players may push beyond normal physical limits. Professor Mike Tipton, a sports and health expert at the University of Portsmouth, said playing in temperatures above 28°C changes the game.
“We see reduced intensity, less sprinting and potentially fewer chances being created,” he said. “As temperatures climb further, the risks also increase.” He said prolonged exposure and dehydration could lead to heat exhaustion or heat stroke.
Those risks are not limited to players. Fans, stadium workers, security staff and broadcasters can also be exposed to dangerous heat, particularly during daytime fixtures and long periods of waiting outside stadiums.
The tournament will be played in June and July, when several host cities are already prone to high summer temperatures.
The 2026 World Cup is expected to be the largest edition of the tournament, with an expanded format and matches spread across North America. Climate Central’s analysis suggests that heat may no longer be a marginal concern for football administrators.
The report argues that climate change is altering the conditions in which major sports events are played, and that scheduling, hydration breaks, medical protocols and venue planning will become increasingly important.
“Unless we stop burning fossil fuels, the future of the competition won’t be about who plays best, but about who can tolerate the heat,” said one expert cited in the analysis.
