Around 25% of the 2026 FIFA World Cup matches are likely to be played in conditions of 26°C Wet Bulb Globe Temperature (WBGT), a heat index that includes temperature and humidity, or higher, a new analysis has warned, raising concerns over extreme heat and player safety.

The study said around five games could take place at WBGT levels of 28°C or above, which is equivalent to about 38°C in dry heat or 30°C in high humidity, a threshold that the global players’ union FIFPRO considers unsafe for play and advises postponement.

Wet-bulb temperature combines heat and humidity measurements to indicate how effectively the human body can cool itself through sweating when outdoors. A wet-bulb temperature of 31 to 35°C can be fatal to humans depending on their exposure, according to scientists.

To avoid the extremes of Qatar’s summer heat, the 2022 FIFA World Cup was held in November and December, becoming the first edition to take place at the end of the year and outside the traditional months of May, June and July. Energy-efficient cooling systems were developed following Qatar’s successful bid for the 2022 World Cup, according to various reports.

The risk of these more extreme conditions has nearly doubled since the 1994 FIFA World Cup as a result of climate change, according to researchers at World Weather Attribution (WWA), a team of climate scientists and experts who focus on rapid attribution studies.

While three venues have cooling inside the arena, over a third of high-risk games are scheduled at venues without air conditioning, including Miami, Kansas City, New York/New Jersey and Philadelphia, according to the analysis.

The analysis reveals that 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. Taking account of actual game times, scientists analysed the likelihood of every one of the 104 FIFA 2026 World Cup matches taking place in conditions exceeding key safety guidelines laid out by FIFPRO.

Around 18 games (nearly one-fifth of the total) are scheduled for open-air stadiums with at least a 1-in-10 chance of heat exceeding 26°C WBGT during play. This includes the final, the third-place playoff and two quarter-finals, the analysis said.

“The calculations to estimate the likelihood of 2026 FIFA World Cup games being played in high WBGT conditions are in line with FIFPRO’s calculations published in 2023. These estimations justify the need for – and implementation of – a series of mitigation strategies with a view to better protecting players’ health and performance when they are exposed to hot conditions,” FIFPRO medical director Vincent Gouttebarge said in a statement.

Climate science professor at Imperial College London Friederike Otto said, “Our research shows that climate change is having a real and measurable impact on the viability of holding World Cups during the northern hemisphere summer. The 1994 World Cup may not feel particularly distant to many adults today, yet half of human-induced climate change has happened since then.”

“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, highlighting the urgent need to realise that there is no aspect of society not affected by climate change,” she added.

“During the 2026 World Cup, heat risk should not be judged by air temperature alone. A 30°C day in dry, breezy conditions is very different from a 30°C day with high humidity, strong sun and little wind. High humidity reduces the evaporation of sweat, limiting the body’s primary cooling mechanism. That is why wet bulb globe temperature, or WBGT, is so important,” consultant anaesthetist at Imperial College Healthcare NHS Trust and clinical senior lecturer at Imperial College London, Chris Mullington, said.

Responding to WWA’s findings, UN Climate Change executive secretary Simon Stiell said on Thursday, “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, which can be a game-changer for people everywhere.”