The 2026 FIFA World Cup, spanning June and July across 16 cities in the United States, Canada and Mexico, is set to be one of the most thermally demanding tournaments in the competition's history. Temperatures in host cities such as Miami, Houston, Dallas and Monterrey can regularly exceed 32 degrees Celsius during those months, and inside a packed stadium of 65,000 fans, conditions can be several degrees hotter still. FIFA has acknowledged the risk, introducing mandatory cooling breaks in each half of every match — a first for a World Cup — and announcing that host cities will provide hydration stations, misting areas and cooling tents outside venues.

Experts warn, however, that these measures may not go far enough. The relevant measure for assessing heat risk is not air temperature alone but the "wet-bulb globe temperature" index, which combines heat, humidity, solar radiation and airflow to estimate the physiological strain on the human body. Elite footballers cover 10 to 13 kilometres per match through repeated sprints and direction changes, generating significant internal heat. Field-based research from the University of Canberra found that players' average peak core temperatures frequently exceed 39 degrees Celsius during competitive matches, and can surpass 40 degrees — a level associated with serious health risk — even in conditions not traditionally classified as extreme and even when cooling breaks are in place. At its most severe, exertional heat stroke is a life-threatening emergency.

The picture is further complicated by gender differences. While women athletes generally reach lower absolute core temperatures than men, standard FIFA-style cooling breaks appear to deliver smaller physiological benefits for female players. Research suggests women gain more protection when in-play breaks are combined with longer half-time periods spent in air-conditioned spaces — an arrangement the current framework does not guarantee.

Meanwhile, a separate but related controversy has surrounded fan welfare. FIFA this week reversed earlier guidance and clarified that spectators may bring one factory-sealed, soft plastic water bottle of up to 590 millilitres into stadiums. Hard-sided and reusable bottles remain banned, with the governing body citing safety and security concerns — items that could be thrown pose a risk in crowded venues. The reversal came after the original prohibition on reusable bottles prompted widespread concern about hydration, particularly at venues where temperatures are expected to exceed 25 degrees Celsius.

Sport scientists and public health experts argue that scheduling is ultimately the most powerful tool available. Afternoon kick-offs, which combine peak solar radiation with high air temperatures, consistently produce the greatest heat strain on players. Evening matches reduce but do not eliminate the risk. Historically, however, broadcast and commercial considerations have driven daytime scheduling at World Cups — a tension that organisers have yet to fully resolve. With climate change making extreme heat events more frequent, researchers stress that protecting athlete and spectator health will require not just better in-game interventions, but a broader willingness to rethink when and where major tournaments are held.