For Norway’s national men’s soccer team, Saturday’s World Cup quarter-final against England will be a first in more ways than one. As the Scandinavian side prepares for the biggest match of its history, it will also face conditions almost unimaginable back home: the punishing combination of South Florida heat, humidity, and blazing sunshine that scientists warn can push the human body to its limits.

South Florida’s mix of strong sun, hot-air temperature, and high humidity—boosted by a plume of dusty air from the Sahara desert sweeping across the Atlantic through the state—will put the northern European players under a level of heat stress rarely experienced in their native countries.

Scientists quantify this heat stress by calculating the wet-bulb globe temperature. On top of air temperature, the index takes into account humidity, which limits evaporation of sweat from the skin; wind, which can act as a coolant; and solar intensity, as sunshine directly raises individuals’ skin and core temperatures.

Saturday’s match is forecast to be played at an extremely high WBGT of around 88 degrees Fahrenheit (31 degrees Celsius). The American College of Sports Medicine recommends that athletic activities cease when this measure exceeds 82 degrees Fahrenheit, because at this level, humans struggle to cool down, and body temperature starts to increase rapidly. FIFA itself stipulates that if the WGBT exceeds 90 degrees Fahrenheit, players and referees need to take breaks after 30 and 75 minutes of play to cool themselves down with ice-water-soaked towels.

While both teams will have been training to adapt to the environment, the conditions could make for a more sluggish match, according to Matt Maley, a researcher in environmental ergonomics and physiology at Loughborough University in the UK. He told WIRED: “At Miami this weekend, we may actually see players reduce the amount of sprints or the distance they cover.” That would be a far cry from the fast-paced Premier League and energetic Eliteserien games English and Norwegian soccer fans are used to watching.

But the real danger is ambition, says Maley. “Motivation does sometimes supersede what the body’s telling the brain, so that’s when we get to the danger area, because people are that motivated to run the same distance, conduct the same amount of sprints, and they could expose themselves to heat exhaustion.”

Miami, among other American locales, has been getting hotter in recent years, as concrete and greenhouse gases released through burning fossil fuels trap heat.

A coalition of scientists across five continents warned FIFA and World Cup participants in May about the increasing medical risks of heat stress. “We are concerned that FIFA’s current guidelines on heat-stress mitigation are inadequate and will place players at risk of heat injury at the 2026 men’s World Cup,” they wrote in an open letter, noting the three-minute hydration breaks are too short for the players to rehydrate and cool. They recommended the hydration breaks be doubled in length and that any match set to take place with a WBGT of 82 degrees Fahrenheit be postponed.

Fans also face dangers, including heat exhaustion, dehydration, and heat stroke from the stadium’s high-heat stress levels, scientists from the New Weather Institute cautioned in a report, adding that older supporters and those with pre-existing health conditions are particularly at risk. They warned: “The 2026 World Cup’s heat stress crisis threatens to transform what should be football’s greatest celebration into a public health emergency.”