At least 25 World Cup matches have been held on days when climate change made high levels of humid heat more likely, as a major heat dome over eastern North America threatens to expose players and supporters to temperatures of up to 35.7°C during the knockout stage.
New analysis by Climate Central found that the heatwave, at its peak, was made at least five times more likely due to climate change. Heat warnings across the eastern United States and Canada have raised concerns over player safety, fan health and the uneven physical burden created by differences in stadium infrastructure.
Teams playing at New York’s MetLife Stadium in New Jersey and venues in Miami, Philadelphia and Toronto, which do not have air conditioning, face hotter conditions than those competing in climate-controlled stadiums in Houston, Dallas and Atlanta. Players progressing from outdoor fixtures could consequently carry a greater physical burden into subsequent rounds.
Infrastructure Divide
Portugal’s match against Croatia in Toronto on July 2 faced a forecast high of 33.8°C, or 8.7°C above normal. The humid heat was made at least seven times more likely due to climate change.
Argentina’s July 3 fixture against Cape Verde in Miami was forecast at 30.3°C, with the humid heat made at least ten times more likely. The Paraguay-France match in Philadelphia on July 4 faces the highest temperature among the identified fixtures, with a forecast of 35.7°C, around 5.3°C above normal. Such humid heat was made at least seven times more likely due to climate change.
England and Mexico have a relatively favourable draw, with a cooler evening match in Mexico City on July 5. Teams scheduled to play in Vancouver on July 7 are also expected to encounter more temperate conditions.
Beyond the Thermometer
“The biggest mistake people make is focusing on the air temperature. That number is measured in the shade. Elite footballers are competing in the heat of direct sunshine while producing huge amounts of body heat through exercise,” said Ollie Jay, Professor of Heat and Health and Director of the Heat and Health Research Centre at the University of Sydney.
“In hot, humid conditions, evaporating sweat becomes their only effective cooling mechanism, and when humidity is high that cooling system starts to fail. The result is physiological strain that is far greater than the weather forecast alone would suggest,” he said.
Jay said heat and humidity at venues such as Philadelphia could have a greater impact on players than altitude in Mexico City.
“Widely quoted metrics like the Heat Index can substantially underestimate what players experience because they were never designed for athletes exercising at maximal intensity in full sun. They assume conditions under which the body can maintain a stable core temperature, and this assumption simply doesn’t hold during elite football in these environments,” he said.
Supporters also face significant exposure even at venues where air conditioning protects players inside the stadium. More than 100 fans were treated for heat-related illnesses in Houston during the group stage, while hundreds of supporters received treatment in Houston and Miami. Fan festivals were disrupted or cancelled in Toronto, Houston and Atlanta.
“For fans, the high temperatures mean heat risk doesn’t end at the stadium gates. Getting to and from the venue, waiting in lines, and tailgating in direct sun can be just as dangerous as time in the stands,” said Luke Parsons, a heat expert at The Nature Conservancy.
“Several of this week’s matches, including those in Houston, Dallas, and Miami, are forecast to occur in conditions where wet bulb globe temperature is expected to approach or exceed thresholds we know push the limits of the body’s ability to cool itself, especially during sustained physical exertion,” he said.
“Outside in the sun, it’s not just uncomfortably hot for sustained intense activity—it’s dangerously hot,” Parsons said.
At least two group-stage matches were played in temperatures exceeding the threshold at which global players’ union FIFPRO recommends postponing or delaying games. The France-Iraq match on June 22 was postponed for two hours due to storms, the first weather-related delay to a World Cup match since 1974.
“I think we can very confidently now say that every heatwave that is occurring today has been made more intense and more likely because of climate change. There is no doubt that climate change is really an absolute game changer when it comes to heatwaves,” said Fredi Otto of World Weather Attribution.