World Cup 2026: Extreme Heat Threatens Players, Scientists Warn

The 2026 FIFA World Cup, hosted by the United States, Canada, and Mexico from June 11 to July 19, could become far more than a global sporting event. About twenty researchers specializing in climate, health, and sport are now sounding the alarm: some matches could be played in dangerously extreme heat conditions for players—and for fans as well.

In an open letter addressed to FIFA, these scientists are calling out health risks that organizers have understated. This historic edition — the first to bring together 48 teams across three countries and 16 host cities — could symbolize the widening clash between elite sport and climate disruption as well.

Matches Under 40°C? Several Host Cities Raise Serious Concerns

Atlanta, Miami, Dallas, Houston, Mexico City… Several host cities of the 2026 World Cup sit among the places most exposed to intense summer heat. In parts of the southern United States and northern Mexico, temperatures routinely top 95°F (35°C) in summer and can climb to 104°F (40°C) during heat waves.
But the real danger comes primarily from humidity. When heat and humidity combine, the human body loses part of its ability to cool itself through sweating. The result: physical exertion becomes much more taxing, even for professional athletes.
According to the World Weather Attribution (WWA) network, roughly one quarter of the 104 matches scheduled could require enhanced cooling measures. Some experts even contend that certain matches should simply not be played under such conditions.

The WBGT Index: the Thermometer That Alarms Scientists

The researchers rely particularly on the WBGT (Wet Bulb Globe Temperature) index, used in elite sports, the military, and certain industrial sectors to measure the real thermal stress endured by the human body.
Unlike a plain outdoor temperature, this indicator accounts for humidity, solar radiation, ambient heat, and air movement. It thus allows a much more precise assessment of physiological risks linked to heat.(1)
Yet several climate projections show that some matches could exceed the critical 28°C WBGT threshold, beyond which specialists deem high-intensity sport dangerous. Severe dehydration, dizziness, heat stroke, cardiovascular problems, or loss of consciousness: the risks are real.
“Climate change now has a measurable effect on the viability of World Cups held in the summer in the Northern Hemisphere,” summarizes Friederike Otto, climate scientist at Imperial College London and cofounder of the WWA.(2)

The Blues’ matches could be played under extreme conditions

The potential schedule for the French team already worries climate and sports-health experts. Some of Les Bleus’ games could be staged in blistering heat in American cities particularly exposed to high summer temperatures.
One notably sensitive matchup is a game slated for Dallas, Texas, where temperatures regularly exceed 95°F in June. Another feared scenario involves a match in Philadelphia in a non-air-conditioned stadium, in the late afternoon, when heat and humidity remain extremely high.
Even knockout rounds could be affected. If France finishes at the top of its group, its Round of 16 could also take place in difficult thermal conditions. As for the tournament final, some experts fear it could occur under a level of heat stress particularly high for both players and spectators.

Fans Are Also Exposed to Health Risks

The danger doesn’t only concern players running more than ten kilometers per match. Tens of thousands of fans could also be exposed to extreme temperatures for hours in sun-drenched stadiums, on transit, or in fan zones.
Scientists remind us that major sporting events are already increasingly disrupted by heat. The Tokyo Olympics, the Australian Open, and certain American football games have already been marked by episodes of intense thermal stress.
With global warming, these once exceptional situations are progressively becoming the new normal.

Cooling Breaks Considered Largely Insufficient

Facing these concerns, FIFA plans mandatory three-minute cooling breaks per half. A move touted as historic by the global governing body of football. But for scientists, that’s far from enough.
Signatories of the open letter call for breaks of at least six minutes to allow a real drop in core temperature and effective rehydration. They argue three minutes do not suffice to cool an organism under intense thermal stress.
Another point of contention: FIFA’s measures would apply only above 32°C WBGT, or four degrees above the threshold considered critical by many experts.
” Science clearly shows that above 28°C WBGT, high-intensity sport can put players at risk,” remind several researchers. For them, continuing to hold certain matches in these conditions would amount to ignoring the consequences of climate disruption.

World Football Caught Up by Climate Change

Beyond the 2026 World Cup, this controversy highlights a broader problem: adapting professional sport to a warmer world. For decades, international competitions have been scheduled according to historic calendars, without truly accounting for new climate realities.
Now, heatwaves force sports federations to rethink practices: shifted kickoff times, climate-controlled stadiums, match postponements, or strengthened medical protocols are gradually becoming essential.
For several climatologists, the 2026 World Cup could become a symbolic turning point. The question is no longer solely about performance, but about the health and safety of players and fans in a world facing increasingly extreme heat.