Football’s global players’ union on 14th May rekindled worries over heat at the 2026 World Cup, with scientists saying there is now a high risk of dangerous temperatures for players and fans.

About a quarter of the 104 World Cup games at the expanded tournament in the United States, Mexico and Canada are likely to be played in conditions beyond the range of safety recommended by FIFPRO, double the odds at the last World Cup in the U.S. in 1994.

The researchers said that about five matches may occur in conditions they call unsafe—they would advise postponing such games.

The scientists evaluated the risk based on the time it takes for the kickoff and Wet Bulb Globe Temperature (WBGT) index, which indicates the body’s cooling capacity.

FIFPRO’s medical director, Vincent Gouttebarge, said, “the calculations for estimating the risk of playing matches in high WBGT conditions in the games scheduled for the 2026 FIFA World Cup are in line with the calculations published by FIFPRO in 2023.”

“These estimates support the need for – and the implementation of – a series of mitigative measures in order to protect the players’ health and performance when they are exposed to hot conditions.”

FIFPRO recommends fans to be used when WBGT is above 26 degrees Celsius and suggests that matches should be postponed when the WBGT is above 28C (around 38C when there is little humidity and around 30C when there is high humidity).

FIFA has implemented heat-risk plans with measures such as three-minute hydration breaks in each half of the game, cooling facilities for fans and players, modified work-rest cycles and improved medical preparations according to the actual situation, it told Reuters.

“FIFA has a responsibility to ensure the safety and well-being of its players, referees, fans, volunteers and staff,” the global body said in a statement.

‘MORE CONSERVATIVE FOOTBALL’

Consultant anaesthetist Chris Mullington at Imperial College London NHS Trust, and clinical senior lecturer at Imperial College London, explained that extreme heat is likely to affect the way games are played, but not likely to cause mass medical emergencies among the players.

“It will be more of a performance issue than a health issue,” he said. “These players are elite athletes and acclimatised. Players will self-pace. That one can not very easily override the thermoregulation behaviourally.”

“So it’s possible you will settle for more conservative football.”

Based on the analysis, there is some mitigation of risk at three of the 16 host venues due to cooling systems.

But over one-third of the games that have a 10% or greater chance of exceeding 26°C WBGT are played at stadiums that do not have air conditioning, such as in Miami, Kansas City, New York, and Philadelphia.

This includes the final at MetLife Stadium in East Rutherford, N.J., where the one-in-eight probability of surpassing the 26°C threshold now stands at about double what it was in 1994, the analysis said, and the odds of hitting the more dangerous threshold of 40°C or more are around 3% compared with 1.5% in 1994.

The results showed the importance for FIFA to rethink countries where World Cups are held in the future, especially in summer, in hot climates, said Friederike Otto, professor of climate science at Imperial College London.

“From a health point of view, it would be advisable to have these (World Cups) ⁠either earlier or ​later in the year, so you can have a football party rather than something that ​is a massive health risk for the whole city,” said Otto.

FIFPRO also cautioned that even though there are air-conditioned stadia like in Dallas and Houston, which will help keep players safe, the stadia will also need to keep fans safe since, at games, they are in the venue for hours, and at outdoor fan festivals, they could be subjected to extended periods of exposure to high temperatures.