Risk of Extreme Heat Stress ‘Very High’ for Footballers at 2026 Fifa World Cup

Footballers face a “very high risk of extreme heat stress” at most of the stadiums that will host the 2026 Fifa World Cup in North America, a new analysis has warned.

2022 was the first time the world’s premier football tournament was held in the Northern winter, with Fifa pushing the World Cup to November-December to avoid the intense heat experienced by Qatar in the summer seasons.

But 2026 will see the Fifa World Cup go back to its traditional summer programming, jointly hosted by the US, Canada and Mexico – where temperatures historically don’t go as high as the Gulf nation’s peak.

That said, we’ve already seen some of the worst heatwaves recorded in North America this year, causing an unprecedented number of deaths and heat-related illnesses, and prompting the US government to propose a national strategy to protect workers from extreme temperatures.

And under a climate-denying president in Donald Trump, these heatwaves will only get worse by the time the 2026 World Cup rolls around, with footballers warned of a “very high risk of extreme heat stress at 10 of the 16 stadiums, according to a new analysis.

The combination of high temperatures, intense physical activity, and the “huge diversity of the biothermal conditions” in the US, Canada and Mexico, will subject footballers to experience varying levels of heat and environmental stress, with certain stadiums in the South contributing to “uncompensable thermal stress” as temperatures cross 49.5°C, the study found.

Heat stress likely at times when matches will be played

The research, published in the Scientific Reports journal, revolves around the risks of severe heat stress and subsequent water losses in footballers, as well as the oxygen content of the air they will inhale.

The scientists calculated hourly values of biometeorological indices at the 16 stadiums, adjusting them with modifications to activity levels, movement speeds and clothing to reflect the level of thermal stress on players during a match.

They suggested that the distances between the individual stadiums reach nearly 5,000km, meaning the matches will be played in nine different types of climates.

The research found that the highest risk of thermal stress is in Arlington and Houston in the US, where there’s a 70% probability of “uncompensable heat stress” between 2pm and 6pm with temperatures exceeding 50°C, as well as Monterrey in Mexico, where the risk exceeds 50% in the afternoon.

In fact, the greatest stress was estimated to occur between 2pm and 5pm at all but one stadium, and in Arlington, Atlanta, Houston, Kansas, Miami and Monterrey, matches will most probably be played between 3pm and 10pm, hours when the “overwhelming majority constituted very strong and extreme heat stress conditions”.

“When performing in warm and humid conditions, players’ heat production from intense physical activity often exceeds their ability to dissipate excessive heat, which may increase the risk of exertional heat illness,” the study stated. “In response to prolonged exercise in a hot environment, intense sweating is triggered, which may result in dehydration of the body.”

It added: “Staying in such conditions may place a heavy burden on the body, result in a partial failure of the body temperature regulation processes and, consequently lead to a rise of the core temperature, followed by the occurrence of heat exhaustion, potentially even heat stroke.”

The author further warned that extreme heat stress during intense physical activity not only impairs athletes’ performance, but also may lead to “overexertion of their body and, in extreme cases, fatalities”.

Experts call for heat policy reform at Fifa World Cups

To determine the safety standards during a football match, Fifa recommends the use of the Wet Bulb Globe Temperature (WGBT) index. If this temperature exceeds 32°C, cooling breaks are mandatory in both halves. But the scientists said this measure underestimates the heat stress levels, as it doesn’t incorporate metabolic heat production or the effects of body movement on air velocity. WGBT also doesn’t properly reflect the thermal load on people when sweat evaporation is limited.

“During matches at the 2026 FIFA World Cup, for the safety of the players, it will be necessary to use treatments that reduce the impact of heat stress, including regular additional breaks for cooling of the body and adequate fluid replenishment,” they concluded, adding that the risk of heat stress should be considered a threat for substitute and supporters too.

The scientists further recommended that tournament organisers optimally plan the time schedule of the matches for each individual venue. The findings, they said, would allow national team training staff to safely prepare players in variable and often unfavourable conditions, as well as adapt pre-match programmes accordingly.

The 2026 World Cup is being sponsored by Saudi Aramco, the state-owned company that also happens to be the largest oil producer on the planet. It was named the world’s largest sportswasher in a recent report, doling out $1.3B in 10 sports deals despite being responsible for 4% of the world’s emissions in the last 60 years.

Saudi Arabia itself could be the host of the 2034 World Cup, and was a key voice in stalling efforts to restate the pledge to transition away from fossil fuels at COP29 in Baku earlier this month. It has appeared to have close ties with Fifa president Gianni Infantino too, who has spoken about his delight at welcoming Aramco as the governing body’s partner.

And earlier this year, similar alarm bells were rung over athletes’ wellbeing at Paris 2024, which were expected to be the hottest Olympics ever. Here, too, football was among the sports associated with a high risk of heat stress.

Julian Périard, the deputy director of the University of Canberra Research Institute for Sport and Exercise who has published Fifa-funded research on preventing heat stress, said the 2026 World Cup study likely underestimated heat stress risk.

“We have also called for the development of a football-specific heat stress policy with actionable categories (e.g. cooling break, cooling break with extended half-time and cooling, postponement/cancellation) that account for the evaporative heat loss requirement of players and the evaporative capacity of the environment, based on the prevailing ambient conditions and player activity and clothing,” he said.

“Such a policy could be implemented at the 2026 World Cup, as well as the 2030 World Cup in Spain, Portugal and Morocco to protect the health of players and the integrity of the game.”