Nine group stage matches at this year's World Cup were contested in potentially hazardous heat and humidity levels, according to new analysis, prompting the global players union to warn that temperature management will become central to how major tournaments are scheduled going forward.
Researchers examined conditions across the 72-game group stage using wet bulb globe temperature (WBGT) readings, which measure the combined effect of heat, humidity, sunlight and wind on human physiology. Matches played at or above 28 degrees Celsius (82 Fahrenheit) exceeded thresholds that the players union, Fifpro, has previously identified as potentially dangerous enough to warrant postponement.
An additional 13 matches may have reached those dangerous levels in cities with open-air stadiums, though they were not included in the count because those venues had air conditioning. The most severe conditions occurred at Miami's Hard Rock Stadium, where Uruguay's draw with Cape Verde on June 21 saw WBGT readings estimated at or above 33 degrees Celsius, surpassing a previous tournament high of approximately 32.9 degrees recorded six days earlier during Uruguay's match with Saudi Arabia.
The WBGT metric matters because it accounts for humidity, wind and direct sunlight in ways simple air temperature cannot. When WBGT climbs high enough, sweat no longer evaporates efficiently from the skin, and the body loses its primary cooling mechanism. The result can be rapid overheating leading to heat illness or death.
Fifpro's response underscores a growing reckoning in professional sports over climate effects. "The lesson for everyone in the industry is that with a warming planet, heat conditions will play a bigger part in tournament and league scheduling decisions in the future," a union spokesman said. The warning extends beyond players to encompass referees, spectators and workers at venues.
FIFA has implemented three-minute hydration breaks at every match this year and scheduled most games for late afternoon or evening hours to avoid peak heat. The organization has also stationed meteorologists at venues and coordinated with local authorities on heat mitigation. But only three stadiums, in Dallas, Houston and Atlanta, feature full air conditioning that can lower WBGT inside the venue itself.
Even air-conditioned stadiums pose risks. Spectators and workers remain exposed to dangerous heat during entry and exit, in parking areas, and on transit platforms. Joshua DeVincenzo, a researcher at Columbia University's National Center for Disaster Preparedness, emphasized the cumulative exposure fans face throughout their stadium experience. "Taking into account their entire journey to the stadiums, arriving early, leaving late, and how much time is spent in heat-conducting spaces like parking lots, cars, trains and platforms, and unshaded areas pose significant risks," he said.
The opening day fan festival in Houston offered a stark illustration of these dangers: more than 100 people required medical treatment, and four were hospitalized.
Immediate conditions are about to intensify. A major heatwave is moving into the American Midwest and Northeast this week, potentially bringing record-breaking temperatures to cities hosting upcoming matches. Philadelphia is under an extreme heat watch from Wednesday through Saturday, while Kansas City is under an extreme heat warning. Host cities with open-air stadiums including Boston and Kansas City could experience their hottest temperatures of the year so far.
FIFA has indicated that matches at WBGT levels above 32 degrees should prompt cooling breaks and consideration of delays or suspensions. Yet the organization has not publicly specified what WBGT threshold would automatically trigger postponement, and it declined to clarify this threshold when asked.
As the tournament progresses, conditions are expected to worsen. According to projections from World Weather Attribution, approximately one match in four will eventually be played under WBGT conditions at or above 28 degrees, potentially including the final, both quarter-finals and the third-place playoff. The 2026 World Cup, scheduled to be held in the United States, is already projected to be the hottest World Cup on record since the tournament began in 1930.
The UN's climate chief Simon Stiell connected the tournament's heat crisis to broader climate change. "More extreme heat is not random, it's climate change, caused by more than a century of burning fossil fuels like coal, oil and gas," he said. "It affects the things we love, like football."
Labor advocates note that workers face equal or greater risks. OSHA considers WBGT readings above 25 degrees dangerous for heavy lifting and manual labor without frequent breaks, a threshold lower than what many World Cup matches have already exceeded.
The heat problem intersects with other extreme weather challenges. France's match against Iraq was postponed two hours on June 22 due to rainstorms, marking the first weather-related World Cup match delay since 1974.
Fifpro welcomed FIFA's visible efforts to align scheduling and venue selection with player health concerns, noting these were lessons carried forward from last year's brutally hot Club World Cup matches in the United States. Yet the union cautioned that expanded tournament formats and stadium infrastructure limitations make it nearly impossible to eliminate heat risks entirely.
Author James Rodriguez: "This is not a temporary problem that scheduling tweaks and hydration breaks can solve. The World Cup is becoming a test case for how major sports will function on a hotter planet, and the answers so far are inadequate."
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