As football’s biggest tournament heads into its decisive knockout stage, another contest is unfolding off the pitch - one against extreme heat.
A sprawling heat dome settling over the eastern United States ahead of the 4th of July weekend is expected to push temperatures to dangerous levels across several FIFA World Cup host cities, exposing thousands of players, supporters, volunteers and stadium workers to sweltering conditions. Scientists say human-caused climate change has made the ongoing heatwave at least five times more likely, turning what was once considered exceptional into an increasingly common feature of global sport. The heat is already changing the tournament. Hydration breaks have become routine. Players are slowing the tempo to conserve energy, substitutions are coming earlier, and cooling towels and ice vests have become as familiar as corner flags. Away from the television cameras, hundreds of supporters have been treated for heat-related illnesses, while fan festivals in several host cities have faced disruptions.
“We’re all watching the game, but it’s stopped, because it’s too hot,” said Simon Stiell, executive secretary of the UN Climate Change Secretariat.
“Hot for players, for fans, for everyone. It’s hot and getting hotter. That’s not random. That’s climate change... Coal, oil and gas are heating our planet. And the health of the game and of our world depends on the choices we make now,” he said.
According to Climate Central, the harshest conditions this week is expected during Paraguay’s clash with France in Philadelphia, where the temperature is expected to soar close to 36 degrees Celsius, a departure of 5.3 degrees. The consequences extend beyond discomfort. Unlike teams playing inside climate-controlled stadiums in Houston, Dallas and Atlanta, players competing in open-air venues such as Miami, Philadelphia, Toronto and New Jersey must battle oppressive heat and humidity before trying to recover for the next round. Scientists say this uneven distribution of conditions could unintentionally create a competitive imbalance, with some teams carrying a heavier physical burden than others. Professor Ollie Jay, director of the Heat and Health Research Centre at the University of Sydney, said the conditions athletes experience are far more severe than weather forecasts suggest. “The biggest mistake people make is focusing on the air temperature,” Jay said.
“That number is measured in the shade. Elite footballers are competing in direct sunshine while generating enormous amounts of body heat through intense exercise. In hot and humid conditions, sweating becomes the body’s only effective cooling mechanism. When humidity is high, that system begins to fail, placing enormous physiological strain on players,” he said. The risk is equally serious for supporters. While players benefit from medical teams, cooling breaks and carefully monitored hydration, fans often spend hours standing in queues, travelling on public transport or gathering in fan zones under direct sunlight. Dr Luke Parsons, a heat expert with The Nature Conservancy, warned that the danger begins well before kick-off. For fans, the heat risk doesn’t end at the stadium gates.
“Getting to and from the venue, waiting in lines and spending time outside can be just as dangerous as being inside the stadium. Outside in the sun, it’s not just uncomfortably hot, it’s dangerously hot,” Parsons said. The warning comes after more than a hundred spectators were treated for heat-related illnesses in Houston during the group stage, while fan events in Toronto, Houston and Atlanta were either disrupted or cancelled because of the weather.
The World Cup has already experienced at least two matches played above the heat threshold at which the global footballers’ union FIFPRO recommends postponement or delay. France’s group-stage match against Iraq was also delayed by two hours, becoming the first weather-related World Cup postponement since 1974. Researchers estimate that climate change increased the likelihood of dangerous wet-bulb temperatures during 25 group-stage matches. Scientists say these events reflect a broader trend rather than isolated weather extremes. “I think we can very confidently now say that every heatwave occurring today has been made more intense and more likely because of climate change,” said Dr Fredi Otto of World Weather Attribution.
Are FIFA’s heat safety rules enough?
Mandatory three-minute hydration breaks midway through each half are to protect players, and referees, from extreme heat illness. But they’ve sparked criticism from different groups: some say they’re interrupting the game’s flow and give coaches a chance to shift momentum in their team’s favor, while some scientists have said the breaks should be longer to allow players to meaningfully cool and rehydrate when heat is extreme.
Matches outdoors during peak heat hours have also been limited, and those expected in warmer windows are prioritized for covered stadiums, FIFA said.
