The World Cup just had one of its hottest matches, in a challenge for the sport

The World Cup just had one of its hottest matches, in a challenge for the sport

Fan favourites Norway could find themselves in trouble when they face England on Sunday in extreme heat. (Reuters: Hannah Mckay)

The World Cup is becoming a test case for sport in a hotter climate as players and fans endure heatwave conditions across North America.

A recent match between France and Paraguay was played in 38C heat and the Norway vs England semifinal is likely to be played in dangerously hot weather in Florida.

Researchers and sports scientists say climate change is likely to force global tournaments to rethink where they are hosted and when matches are played.

As football's greatest sporting rivalries are on show at the World Cup, a common enemy is stalking athletes and players of all stripes in equal measure: heat.

North America is still in the grips of a record-breaking heatwave.

Those tuning into tomorrow morning's World Cup semifinal between Norway and England can expect a rather sweaty affair, with the "feels-like" temperature in Miami expected to hit 43 degrees Celsius.

There is even talk that heat protocols could result in the game being postponed, but that seems unlikely given the television ratings on the line.Last Sunday, players slogged their way through what is being called one of the hottest games in the tournament's history, when France squared off against Paraguay in Philadelphia amid early evening temperatures hovering around 38C.

France goalkeeper Mike Maignan hydrates ahead of his World Cup match against Paraguay. (AP: Martin Meissner)

It follows searing conditions during the group stage games, nine of which met global players' union FIFPro's thresholds for delay or postponement.

The only two matches thought to be hotter than France vs Paraguay were played in broad daylight over 30 years ago at the first American World Cup, when temperatures on the field reportedly reached 43C and 48C in Florida and Texas respectively.

The pitch and rafters of Philadelphia Stadium were almost certainly hotter than the forecast, with on-field temperatures possibly exceeding 43C.

"Especially for these outdoor stadiums, [you have] a restriction of airflow … so when you're on the pitch, you're not really getting the natural wind … you've got the direct sun beating down on the pitch," said Climate Central meteorologist Shel Winkley.

Body heat radiating from tens of thousands of fans and the stadium itself, composed of concrete and steel, also contributed.

"You're essentially making this little microclimate inside of what is a bigger dome of heat that we experienced over Philadelphia," he said.

Players were not the only ones feeling the heat ahead of Paraguay vs France. (Reuters: Jeenah Moon)

What has led to this exceptional heat? The answer, according to Mr Winkley, is climate change driven by human activities.

"We knew that going into this match, there was an over 60 per cent chance that [the athletes] would experience some sort of performance-impairing heat, which is a temperature of above [28C]," he said.

"We know that with the carbon emissions we've put into the atmosphere, that those percentage points were raised by about 17 per cent.

The heat conundrum is something organisers are keenly aware of and have taken steps to manage better this time around.

Artificial turf has been banished, mandatory three-minute hydration breaks introduced and, to the detriment of millions of European viewers, no matches have been scheduled in Florida before 5pm.

Games in Texas are being played in expensive, climate-controlled stadiums.

Football governing body FIFA's own rules dictate play should be reconsidered when the wet-bulb temperature, a measure that takes the cloistering effects of humidity into account, reaches 32C. The player's union argues it should be lower.

Researchers at the 2014 World Cup in Brazil found the sweet spot for an elite footballer's performance was lower humidity weather, below 22C. The worst was 28C and above.

Hydration breaks have been an unpopular addition among fans who argue they ruin the flow of the game. (Reuters: Amanda Perobelli)

Scientist Matt Brearly, who served as the heat specialist for the Australian Olympic Team at Beijing in 2008, says professional athletes are much better at dealing with temperatures that would send average people to the emergency department, but there are limits.

"We start to see their performance be impaired … if they're playing man on man, they may start to zone off and you see them limiting their physical exertion," he said.

"That's the brain controlling them saying, 'We can't keep producing this much heat, we're overheating.'"

Lewis Miller takes a drink during Australia's clash with Japan. Added drinks breaks will be mandatory at the 2026 World Cup. (Getty Images: James Worsfold)

Telltale signs a footballer might be experiencing heat stress include drooping, slouching and stumbling around the pitch. They will have difficulty communicating with teammates.

"And ultimately, if that isn't enough for them to be substituted and they continue to expose themselves and continue to produce heat, they'll collapse," Dr Brearly said.

The future of World Cup tournaments

Qatar's winning bid to host the 2022 tournament, in a flat barren desert, was widely panned among fans as the ultimate symbol of FIFA's corruption.

How on earth could a football tournament be held in summer in a desert, so the thinking went.

The answer, move it to winter, up-ended the schedules of premier leagues the world over.

The deeply unpopular decision is set to be repeated for the 2034 tournament in Saudi Arabia.

But in the future it may have to be repeated for host nations outside of the Gulf.

Conditions are even hotter at this World Cup than in Qatar and those expecting a reprieve at the next one may need to adjust their expectations.

It is due to be co-hosted over the same period in 2030 in Southern Europe, currently dealing with its own record-breaking heatwaves, and Morocco.

Climate-related weather delays can have economic ramifications and negatively affect the fan experience. (AP: Seth Wenig)

These quandaries are not limited to the World Cup. A warmer planet has the potential to change how billions of fans experience their favourite sports.

"If we continue to experience the trends that we're on, can we safely play the games outside, or do we need to start investing in more infrastructure that brings these games inside?" Mr Winkley said.

Turkish tennis player Zeynep Sonmez helps a ball girl after she collapsed in the heat at the 2026 Australian Open. (Reuters: Edgar Su)

Dr Brearly said hot weather's effect on sport had been gradual.

"I call it climate creep sometimes because the term climate change, people say, 'Well, has it changed?'" he said.

"It hasn't changed, it's creeping along.

"Thirty years ago [spectators in the Northern Territory] could watch a game of football and even the day games weren't too bad in the shade.