A crucial World Cup knockout match between France and Paraguay in Philadelphia this Saturday is set to become one of the tournament’s hottest, raising serious health concerns for players, tens of thousands of fans, and the wider region.
The fixture coincides with a severe heatwave gripping the eastern and central United States, where peak heat indexes are forecast to reach a dangerous 100 F to 115 F (37.78 C to 46.11 C), according to the National Weather Service. High overnight temperatures are expected to offer little respite, with records potentially being broken.
Concerns over extreme heat have intensified throughout the tournament, particularly after French players resorted to field sprinklers to cool down during their earlier match against Sweden in New Jersey, where temperatures hit 90 F (32.22 C).
Scientists have increasingly labelled Fifa’s heat safety guidelines as “inadequate” and “impossible to justify”, even for heat-acclimatised athletes, warning that spectators could face slower, less intense games.
The escalating heat crisis is inextricably linked to climate change. The world has warmed by approximately 1.26 F (0.7 C) in the three decades since the US last hosted the World Cup, according to climate monitoring group Berkeley Earth.
This global temperature increase intensifies and makes heatwaves and other severe weather events more frequent. Scientists from the World Weather Attribution group stated on Friday that the humid heat currently engulfing parts of the US and Canada would have been “virtually impossible” without climate change.
This is not the first time extreme temperatures have plagued football’s premier tournament. The 2022 World Cup in Qatar was controversially moved from summer to winter due to the severe heat threat, and last year’s Club World Cup also saw soaring temperatures.
The global union for professional footballers has repeatedly warned that extreme heat will likely pose an even greater problem at this and future World Cups, recalling the 1994 World Cup game in Orlando, Florida, which saw temperatures reach 110 F (43.33 C).
Heat presents a profound danger to athletes, impacting them both from their environment and from their bodies’ internal warming during exercise.
This dual assault makes it significantly harder to cool down in hot and humid conditions, explains Bharat Venkat, director of the Heat Lab at the University of California, Los Angeles.
“So when you’re exerting yourself on a particularly hot day, the likelihood of experiencing heat related illness or even death is much higher,” he cautioned. Intense physical exertion in scorching conditions can lead to extreme fatigue, impaired performance, headaches, irritability, nausea, dizziness, cramping, and dehydration – all symptoms of exertional heat illness.
Exertional heat stroke, which demands immediate medical attention, stands as the third leading cause of death amongst athletes.
Ryan Calsbeek, a professor of biological sciences at Dartmouth College, highlights that when the wet bulb globe temperature (WBGT) – a measure incorporating temperature, humidity, cloud cover, and wind – surpasses approximately 95 F (35 C), individuals lose their ability to cool rapidly, and “the physiological mechanisms just break down.” He added that heat-induced confusion could also compromise a player’s decision-making, potentially influencing a match’s outcome.
Fifa’s current heat safety protocols, including mandatory three-minute hydration breaks midway through each half, have drawn criticism. While intended to protect players and referees from extreme heat illness, some argue they disrupt the game’s flow and offer coaches tactical advantages.
Conversely, some scientists contend these breaks are too short to allow players to meaningfully cool and rehydrate in extreme conditions.
Furthermore, whilst matches outdoors during peak heat hours have been limited and those in warmer windows prioritised for covered stadiums, Fifa’s guideline for postponing a match – only if the WBGT reaches 89.60 F (32 C) – has been widely challenged.
Douglas Casa, CEO of the University of Connecticut’s Korey Stringer Institute, noted that this temperature is “so extreme that in the military, at our basic training facilities in America, if it reaches 32, it’s black flag and all training has to be canceled and stopped.”
With temperatures forecast to exceed 100 F (37.78 C) for Saturday’s game, the players’ union Fifpro and the American College of Sports Medicine have advocated for matches to be delayed at a lower, safer threshold of 82.40 F (28 C).
Despite these challenges, teams are employing strategies to mitigate heat stress. Guilherme Passos, a sport scientist with the Brazilian Football Federation, monitors and prepares Brazil’s national team for extreme heat.
He has helped the team acclimatise to the US heat, advising against exposing them “straight to the hottest time of the day” to maintain training quality, and utilising saunas or hot baths for heat training during competition.
Passos observed that during the 2014 World Cup in Brazil, players covered less distance and reduced high-speed running, instead focusing on technical and tactical precision. Calsbeek emphasised that football players’ unique blend of endurance, explosive speed, and critical decision-making are all severely impacted by temperature.
However, the risks extend beyond the pitch. Many football fans, often consuming alcohol, will be watching the World Cup in these dangerous conditions.
Cities and stadiums have responded by increasing access to shade, cooling areas, water, and deploying medical personnel at Fifa Fan Festivals and around venues. Yet, Calsbeek warns, “People are going to be dehydrated, super excited, and not wanting to leave the match. We’re likely to see, in those extreme temperatures, spectators pay the price as well.”
