Over half of 2026 World Cup stadiums 'dangerous' for players due to heat, study finds

A new study warns that more than half of the stadiums slated to host the 2026 World Cup could pose a significant health risk to players due to extreme heat stress. The research, published in Scientific Reports, simulated climate conditions across all 16 host cities, identifying nine locations as having a very high risk for athletes competing at peak intensity.

The findings suggest the 2026 World Cup could be more than just a sporting event; it may become an unprecedented physiological test. Heat stress occurs when the body struggles to regulate its temperature under excessive environmental heat. For athletes engaged in high-intensity activity for 90 minutes, this can lead to fatigue, dizziness, dehydration, muscle cramps, heat exhaustion, and even increase the risk of cardiovascular events in those with underlying conditions.

Researchers utilized the Universal Thermal Climate Index (UTCI) and factored in the heat generated by players' muscles during matches, a crucial element often overlooked in traditional assessments. "Football is not a normal outdoor walking activity," explained Dr. Katarzyna Lindner-Cendrowska, the study's lead author. "When playing at high intensity, muscles generate a huge amount of heat inside the body. This is a factor that must be taken into account when assessing heat stress risk."

The nine cities identified as most concerning are Arlington, Houston, Kansas City, Miami, Monterrey, Guadalajara, Philadelphia, Boston, and New York/New Jersey. Arlington, Houston, and Monterrey are considered the most critical, with physiological heat indices potentially exceeding 49.5 degrees Celsius during the hottest parts of the day. The study estimates players could lose over 1.5 kilograms of water per hour without effective thermal control measures.

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Football is not a normal outdoor walking activity. When playing at high intensity, muscles generate a huge amount of heat inside the body. This is a factor that must be taken into account when assessing heat stress risk.