A significant heat wave is poised to make Saturday's World Cup knockout round game between France and Paraguay in Philadelphia one of the hottest matches of the tournament, raising concerns for player and spectator safety. Forecasters predict heat index values between 100 F and 115 F (37.78 C to 46.11 C) across the eastern and central United States, with little relief expected overnight.
Concerns regarding extreme heat during the World Cup matches in the U.S., Canada, and Mexico have been growing for months. Scientists have indicated that FIFA's existing heat safety guidelines may be insufficient. Earlier this week, French players were seen using field sprinklers to cool off during a match in New Jersey as temperatures reached 90 F (32.22 C).
Global temperatures have risen approximately 1.26 F (0.7 C) over the last three decades, a period during which the U.S. last hosted the World Cup. Climate scientists attribute the current humid heat wave, affecting parts of Canada as well, to climate change, stating it would have been "virtually impossible" without it.
Physicians and scientists warn that intense exercise in extreme heat and humidity significantly increases the risk of heat-related illnesses, which can range from extreme fatigue and impaired performance to heat stroke, a potentially fatal condition. The wet bulb globe temperature, which accounts for temperature, humidity, cloud cover, and wind, is a key indicator. When this metric exceeds approximately 95 F (35 C), the human body's ability to cool itself can break down. Confusion induced by heat could also affect players' decision-making on the field.
FIFA has implemented mandatory three-minute hydration breaks midway through each half to mitigate heat risks. However, these breaks have drawn criticism, with some arguing they disrupt game flow and offer tactical advantages, while others contend they are too short for adequate cooling and rehydration. FIFA also stated that matches during peak heat hours are limited and that warmer venues are prioritized for covered stadiums.
FIFA's guidelines suggest a match could be postponed if the wet bulb globe temperature reaches 89.60 F (32 C). However, experts note that this threshold is considered extremely high, with military basic training in the U.S. canceling all outdoor activities at this level. The players' union FIFPRO and the American College of Sports Medicine have called for matches to be delayed if the temperature reaches 82.40 F (28 C).
Sports scientists are working to acclimate teams to the U.S. heat. Methods include heat training through saunas or hot baths to maintain training quality and performance. When Brazil hosted the World Cup in 2014, players reportedly covered less distance and reduced high-speed running, focusing instead on technical and tactical precision. Soccer players' dual need for endurance and explosive speed, combined with critical decision-making, makes them particularly susceptible to temperature impacts.
Spectators also face risks. Increased alcohol consumption and intense excitement in hot conditions can lead to dehydration. Cities and stadiums have increased access to shade, cooling areas, water, and medical personnel to address potential issues among fans.