By sports medicine's own heat standard, half the dress rehearsal should have stopped

As the 2026 World Cup gets underway across stadiums in the United States, Canada, and Mexico, researchers studying heat and athletic performance are pointing to a specific data point from last year's Club World Cup, hosted across many of the same US venues, as a preview of the risk this tournament faces [s1].

The benchmark: FIFA's own heat threshold

FIFA defines extreme heat risk using the wet bulb globe temperature (WBGT) scale — a measure that, unlike a simple air-temperature reading, accounts for humidity, wind, and radiant heat to better capture how hot conditions actually feel to a body working hard outdoors. FIFA's own threshold places extreme risk at a WBGT near, at, or above 32°C [s1].

What last year's Club World Cup showed

Researchers examining the 2025 Club World Cup — held in many of the same US stadiums that will host 2026 World Cup matches — found that 31 of 57 matches, or 54%, were played at a WBGT of 28°C or higher [s1]. Thirteen of those matches reached 30°C or higher, and two hit FIFA's own 32°C extreme-risk threshold [s1]. Applying American College of Sports Medicine heat-safety standards to that same set of matches, the researchers concluded that the 31 matches played at 28°C or above "should have been cancelled" under those guidelines [s1].

What the heat did to how the game was played

The data isn't only about athlete safety in the abstract — it showed up directly in performance. Researchers found that the higher the WBGT or ambient temperature climbed, the lower the distances players covered at all speeds during a match [s1], a documented, measurable decline in output tied directly to heat exposure rather than a subjective sense that players "looked tired."

How some venues are managing it, and others aren't

Venue design is already producing a wide gap in conditions among 2026 host cities. Atlanta's stadium, played under a closed roof with air conditioning, maintained a temperature of 22°C regardless of outside conditions [s1] — a controlled environment unavailable to open-air venues in cities including Toronto, Washington D.C., Los Angeles, and Nashville, all of which are hosting matches this tournament [s1]. That gap echoes the 2022 Qatar World Cup, where seven of the eight stadiums used air conditioning specifically to manage extreme desert heat [s1] — a level of climate control largely absent from most 2026 venues.

The protocol currently in place

FIFA's current heat-mitigation measure for matches is a mandated three-minute hydration break midway through each half [s1]. Researchers studying the issue, including Toby Mündel, a Canada Research Chair at Brock University, and Samuel Penna Wanner of the Universidade Federal de Minas Gerais, point to match scheduling — specifically, matches played during afternoon hours in North American summer conditions — as creating the tournament's highest-risk windows regardless of what in-match cooling measures are in place [s1].

What this means heading into the tournament

The Club World Cup data offers something usually missing from pre-tournament heat discussions: an actual dress rehearsal, played across many of the same stadiums, under broadly similar summer conditions, with measured outcomes rather than a forecast. Whether FIFA adjusts scheduling, expands cooling breaks, or otherwise changes its current heat-mitigation approach for the matches remaining in this tournament is an open question the available reporting does not resolve — what's established is the baseline risk profile the 2025 tournament already demonstrated, and the gap between that data and FIFA's own extreme-heat threshold.

Sources

• Should FIFA be doing more to protect soccer players from the World Cup heat? — The Conversation, 2026-06-01