As soccer players and enthusiasts pour into North America for the FIFA World Cup 26™ this summer, the heat will come sweeping in on their heels. The renowned tournament — which will run from June 11 through July 19 across the United States, Mexico, and Canada — is being held during several of the continent’s hottest months, raising concerns for athletes and spectators alike.
While some of the World Cup’s matches have been scheduled to avoid peak temperatures, Bryant University Biological and Biomedical Sciences Lecturer Benjamin Fry notes that others will most likely be played in conditions that will pose a high risk for heat stress — and concerns extend beyond the time of day.
“The problem isn’t just the air temperature at noon versus 7 p.m.,” says Fry, who is also the field experience coordinator for Bryant’s Exercise and Movement Science program and an exercise physiology research fellow for the U.S. Army Research Institute of Environmental Medicine. “It’s the total heat load on the body.”
Monitoring high temps
When it comes to monitoring heat stress and conditions that could impact human health during extreme heat, sports officials will often consult the Wet-Bulb Globe Temperature (WBGT), says Fry, which accounts for ambient temperature, humidity, and radiant heat, including residual heat from the concrete and steel stadiums.
Fry explains that FIFA — the World Cup’s governing body — has historically authorized cooling breaks when the WBGT reached or exceeded 89.6 degrees Fahrenheit. Player’s unions, however, have argued that the risk is already substantial once the WBGT reaches between 82 and 83 degrees Fahrenheit.
“Above those thresholds, you see faster rises in core temperature, accelerated dehydration, reduced repeated-sprint capacity, compromised decision-making, and a marked increase in exertional heat illness risk in players,” Fry says.
How the body reacts
From a physiological standpoint, well-trained, heat-acclimated athletes can safely tolerate higher core temperatures than the general public, notes Fry. For instance, in competitive field sports, it is common to see players’ average core temperatures hit the 101 to 103 degrees Fahrenheit range during match play — with peaks around 104 and 105 degrees Fahrenheit in hot, humid conditions — without overt heat stroke when hydration and cooling are adequate.
“The key concern is preventing a player’s core temperature from climbing above 104 and 105 degrees Fahrenheit for prolonged periods because, beyond that point, the risk of central nervous system dysfunction and exertional heat stroke rises steeply,” Fry says, noting that FIFA World Cup 26™ has changed its cooling break policy to include a mandatory three-minute stoppage at the 22-minute mark of each half in all matches.
Heat acclimation, he adds, can shift the “risk curve” in athletes’ favor, but only to a point. With seven to 14 days of structured training in the heat, players can increase plasma volume, start sweating earlier and more efficiently, and reduce cardiovascular and thermal strain at a given workload, giving them some — but not total— heat resistance.
“That usually translates into lower core temperatures and heart rates for the same match intensity, but it does not make them ‘heat proof,’ especially when matches are played in back-to-back fashion in hot, humid cities with heavy travel and limited recovery time,” Fry states.
Heat for players versus fans
Fans face a different risk profile when it comes to the heat, Fry notes. For players, the primary concern is exertional heat illness and a potential progression to heat stroke if core temperatures exceed about 104 to 104.5 degrees Fahrenheit. For fans, who are generally less fit and less acclimated to the heat, potential major issues could include fainting, heat exhaustion, and cardiovascular decompensation even at much lower internal temperatures — especially when they’ll be sitting for hours in full sun with restricted airflow and limited access to shade or fluids.
Practically, Fry says, this means that more than just clever scheduling will be needed to keep players and fans safe.
“Teams should be planning for early arrival and dedicated heat-acclimation blocks, aggressive hydration strategies, pre-cooling and half-time cooling efforts (including ice towels, vests, and cold fluids), and individualized monitoring for players with prior heat illness,” notes Fry.
Additionally, organizers should anticipate significant potential risk to spectators in the hotter venues and prioritize shade, water availability, and rapid on site medical response as part of their core safety infrastructure.
“The World Cup’s heat management will serve as a test of sport’s adaptation to climate variability,” Fry says. “It highlights how elite events increasingly need to integrate environmental and physiological science into planning to preserve both athlete performance and public safety.”