On a midsummer day in Miami, temperatures can exceed 32°C with high humidity. In a full stadium of 65,000 fans, it can be several degrees hotter, posing a potential health risk to players.
These are the conditions some teams will endure at the 2026 FIFA World Cup in June-July, the hottest months across much of North America.
FIFA has already acknowledged the risk, introducing cooling breaks in each half of all matches for the first time at a World Cup.
But is this enough to protect players in the heat?
It’s not just the high temperatures
When we talk about heat stress in sport, we are not just referring to air temperature.
What matters for the human body is a combination of heat, humidity, solar radiation and airflow – often summarised by the “wet-bulb globe temperature” index, originally developed in the 1950s to curtail heat illness during military training.
Soccer presents a particular challenge under high wet-bulb globe temperature conditions. Elite players routinely cover 10-13 kilometres per match, repeatedly sprinting, decelerating and changing direction.
This produces substantial internal metabolic heat, while opportunities for heat loss are limited by clothing, match structure, restricted access to shade, airflow or other cooling technologies.
If heat production exceeds heat loss, core temperature rises. This places more strain on the cardiovascular system, elevates perceived effort, impacts performance and increases the risk of exertional heat illness, which can include ailments such as muscle cramps and heat exhaustion. At the extreme end, exertional heat stroke, a life-threatening medical emergency can develop.
What the forecasts show for 2026
Analyses of historical weather data across the 16 World Cup host cities indicate heat stress will be common, particularly for afternoon kick-offs in cities such as Dallas, Houston, Miami, Kansas City and Monterrey.
While some venues such as Dallas, Houston and Atlanta have retractable roofs that can modify temperature and airflow, most matches will be played in open-air stadiums, exposing players to heat stress.
Later kick-offs may only offer limited relief, especially in humid environments where sweat evaporation is impaired.
Until recently, most evidence on heat strain in professional soccer came from experimental simulations. Unpublished field-based research from our laboratory at the University of Canberra, measuring core temperature during real professional matches, provides insight into what players experience during competition.
Our data show that during competitive match-play:
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average peak core temperature often exceeds 39°C, rising progressively before half-time or full-time
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players’ peak core temperature can exceed 40°C even in conditions that would not traditionally trigger extreme heat policies and in some cases even when cooling breaks are applied.
Importantly, these observations were documented in elite Australian A-League players who are fit and seasonally heat-acclimatised.
Taken together, this shows elite soccer players can reach and sometimes exceed a 40°C core temperature during matches at wet-bulb globe temperatures that are already considered “high risk” for exertional heat illness.
Read more: Curaçao and Cabo Verde are into the World Cup. What impact can these ‘minnow nations’ make?
Are cooling breaks enough?
Cooling breaks are a sensible and evidence-based safeguard and FIFA’s decision to mandate them in every match at the World Cup is a proactive step.
Cooling breaks – particularly when combined with cold fluid ingestion and ice towels – can lessen rises in core temperature, heart rate and perceived effort, especially in male players.
However, two important caveats remain.
First, cooling breaks do not prevent large rises in core temperature – they reduce the rate or magnitude of that rise. Even with breaks, players can still reach very high core temperatures.
Second, emerging evidence indicates cooling breaks affect women differently. Although women athletes generally reach lower absolute core temperatures than men during match-play, standard FIFA-style cooling breaks appear to provide smaller additional reductions in physiological strain.
Women get more benefits when in-play cooling breaks are combined with longer half-time breaks, which include cooling in air-conditioned spaces.
In short, universal cooling breaks may help but are unlikely to be sufficient on their own.
What are other sports doing?
Most heat policies in sport rely solely on environmental measures such as the wet-bulb globe temperature index. While useful, these metrics describe the weather, not the physiological strain experienced by players.
Several sports have begun to anchor heat policies to the predicted rise in core temperature, linking environmental conditions and sport specific characteristics – heat production and clothing – rather than relying on environmental conditions alone.
This approach focuses on the body’s ability to maintain thermal balance through sweating – something administrators may increasingly need to consider as matches are played in hotter and more humid conditions.
World Rugby uses a similar approach, but tailored to the sport’s demands and clothing worn, as does Sport Medicine Australia for a variety of recreational sports.
Timing matters, a lot
One of the most effective heat-mitigation strategies requires no ice, no towels and no new technology: avoid playing at the hottest time of day.
Afternoon kick-offs consistently produce the greatest thermal strain because they combine peak solar radiation with high air temperature. Evening matches reduce – but do not eliminate – risk, particularly in humid cities.
From a player safety perspective, match scheduling may be as important as in-game cooling strategies. Yet broadcast considerations have historically driven afternoon kick-offs at World Cups.
An ongoing problem
Heat stress is already being reported more frequently in domestic soccer leagues, continental tournaments and youth competitions.
Heat policies must keep pace with a warming climate.
Protecting player health will require earlier decisions, stronger mitigation strategies and a willingness to rethink when and how matches are played – not just at World Cups, but at all levels of the sport.
This article was originally published on The Conversation. Read the original article.
