Sweaty, shirtless football players lying on the pitch have seldom raised eyebrows as they did last week when photographs of European players struggling to train in the heat sparked concerns over sweltering US summer temperatures at the World Cup.

Scientists have long cautioned that extreme heat could disrupt sporting events. Last month, climate experts warned that one in four World Cup games could be played in very hot conditions, affecting fans and players alike.

Those warnings materialised last week; social media was abuzz with sunburnt players — mostly from European teams used to cooler climates — dousing themselves with water to cool off. Norway’s team even opted to wear ice collars around their necks during the friendly against Morocco.

But England captain Harry Kane quickly dismissed speculation over how much the heat would affect players, saying it “won’t be a factor”, thanks to his team’s World Cup training regimen.

So, how much will higher temperatures actually affect players at the World Cup? Al Jazeera takes a look.

What have experts said about heat during World Cup matches?

Th 2026 World Cup could be the hottest on record since the tournament began in 1930 due to a sharp rise in global temperatures, explained Al Jazeera weather presenter Everton Fox.

“Around half a dozen of the venues are prone to extreme heat; places like Dallas, Houston, Miami and the Mexican venues are all likely to swelter,” Fox said.

Daytime temperatures there are expected to average 28C, though the stadiums in Dallas, Houston and Atlanta have air conditioning.

Approximately 26 of the 104 matches could reach at least 26C in the Wet Bulb Globe Temperature (WBGT) index — which measures how effectively the body can cool itself — while five games are expected to be played in conditions of 28C WB or higher, according to World Weather Attribution (WWA), a network of climate scientists.

Of those 26 matches, 17 will be played in stadiums with cooling systems, reducing risks for players and fans.

But more than a third of the games with a one in 10 chance of exceeding 26C will be in venues without air conditioning.

How do hotter temperatures impact athletes’ performance?

Heat stress due to increased humidity, exposure to solar radiation and the effects of wind speed will impact players running around in direct sunlight, Fox said.

“All this makes it harder for the body to cool down as it becomes harder for sweat to evaporate as quickly,” said Fox, a senior meteorologist with more than 30 years of experience.

Physical performance coach Raiyan Abbasi explained that, although the body sweats to achieve thermoregulation – a process that allows the body to maintain its core internal temperature – excessive sweating due to heat could lead to dehydration, cramps and increased fatigue.

Are athletes used to such high temperatures?

“Yes, the majority of athletes will know how to deal with this kind of heat since they’re elite players training and competing in various conditions,” said Abbasi, who has worked as a physical performance coach for British clubs Swansea and West Ham, as well as the Pakistan national side.

Teams will have a performance coach and medical staff to make sure players are ready for the tournament, including through acclimatisation, Abbasi explained – echoing what Kane said over the weekend after his side beat New Zealand 1-0 in Tampa, Florida, where temperatures soared beyond 30C.

Do athletes from hotter nations have an advantage?

World Cup nations whose players train in hotter climates may have a slight advantage when it comes to adjusting to high temperatures in the US.

“But essentially, countries that prepare and perform well can minimise that difference,” Abbasi said, adding that heat can be used positively too.

“Heat is a significant factor in creating good athletes; one way to improve athletic capabilities is to train in the heat.

“It can make big adaptations in your body to improve body temperature.”

Could the World Cup have been held before or after summer in the US?

Fox noted that international tournaments are traditionally in the European domestic off season, which is when the 2026 World Cup is being held.

“Ideally, US weather is most conducive in the spring and autumn, but you’d then be looking at the tornado season in spring and hurricane late summer through autumn before you even begin to think about their domestic sports which locals have more interest in,” Fox said.

What measures has FIFA taken for players and fans?

FIFA said it has carried out heat-risk planning, with measures including three-minute hydration breaks in each half of games, cooling infrastructure for fans and players, adapted work-rest cycles, and enhanced medical readiness that scale according to real-time conditions.

“The hydration breaks probably need to be longer to gain full benefit, but then you risk turning it into a game of four quarters,” Fox said jokingly, although he argued that FIFA could have confined games to northern parts of the US and Canada.

FIFA has also delayed kickoff times for some matches to start outside the hottest afternoon hours.