Scientists warn football’s governing body that global warming has increased risk of extreme hit since 1994 US World Cup.

Climate experts have challenged FIFA after a warning that one in four World Cup games could be played in very hot conditions because global warming has increased the extreme heat risk since the US last hosted the tournament in 1994.

Overheating concerns had already prompted FIFA to mandate a cooling break during each half of World Cup matches. They will be played in 16 stadiums across the United States, Mexico and Canada from that will take place between June 11 to July 19.

“Players and fans face a much higher risk of gruelling heat and humidity at the 2026 World Cup compared to the 1994 tournament on the same continent,” said World Weather Attribution (WWA), a network of climate scientists.

WWA’s scientific analysis estimates that 26 of the 104 matches could be played where temperatures reach at least 26C in the Wet Bulb Globe Temperature (WBGT) index. It measures how effectively the body can cool itself in heat, humidity, sun exposure and wind.

At 26C WBGT, the international footballers’ union FIFPRO recommends cooling breaks as heat strain becomes a real risk for players.

Of those 26 matches, 17 will be played in stadiums with cooling systems, reducing risks for players and fans.

During the 1994 World Cup hosted by the United States, 21 games would have been expected to reach a similar heat threshold, according to WWA.

Five games are expected to be played in conditions of 28C WBGT or higher, a level that FIFPRO says should lead to the delay or postponement of matches until conditions are safer for players and fans.

That risk has nearly doubled compared to the 1994 World Cup.

“It’s dangerous for players, but of course there are also the fans who might gather outdoors, and they are at even more risk because they will not be taken care of by a lot of medical doctors,” said Friederike Otto, WWA co-founder and climate science professor at Imperial College London.

Three of the 16 stadiums – in Dallas, Houston and Atlanta – have air conditioning.

But more than a third of the games with a one in 10 chance of exceeding 26C will be in venues without air conditioning.

The final, on July 19 at MetLife Stadium in New Jersey, has a one in eight chance of seeing 26C WBGT conditions, and a 2.7 percent risk of 28C, according to WWA.

“That the World Cup Final itself – 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,” Otto said.

The executive secretary of UN Climate Change, Simon Stiell, lent his voice to the warning.

“The risk of dangerous heat has doubled” since 1994, which will put “players and fans at risk”, he said on social media.

“We must move faster to protect the game we love and everyone who watches it. That means doubling down on the decisive shift to clean energy.”

FIFA has outlined the preventive measures planned for the World Cup.

“FIFA will continue to monitor conditions in real time, integrating Wet Bulb Globe Temperature and Heat Index surveillance, and stands ready to apply established contingency protocols should extreme weather events occur,” said FIFA, among other safeguards.