Low-Tech Cooling Strategies for Extreme Heat

As the FIFA 2026 World Cup starts, concerns about extreme weather and heat have been at the forefront of the host cities' minds as they prepare to welcome massive crowds for the global event. This year, the World Cup games are taking place this June and July across the United States, Mexico, and Canada – with the U.S. representing a majority (11 of the 16) total host cities across the three North American countries.

Climate scientists and experts warn that extreme heat poses increased risk to athletes, fans, workers, and officials of serious heat illness at the games, especially in July which is the hottest month of the year on average in the contiguous U.S. according to the National Oceanic and Atmospheric Administration.

Exposure to extreme heat, exacerbated during physical exertion, can lead to dehydration, nausea, headaches, heat strokes and, in extreme cases, death. Additionally high humidity combined with strong sunlight and little wind – a climate seen in the majority of the host cities, especially in the southern United States and Mexico – reduces the ability to evaporate sweat and greatly limits the body’s primary cooling system.

Wet bulb globe temperature (WBGT) is the measurement used by sports governing bodies to assess the combined effects of temperature, solar radiation (direct sunlight), humidity, and air movement on human heat stress. All four factors influence the body’s ability to regulate internal temperature through sweating and heat exchange, and the heat category determined from the WBGT is used to guide work-to-rest ratios and fluid replacement strategies for athletes, workers, and spectators.

Guidance from the global players’ union (FIFPRO) recommends that when WBGT reaches 26°C (78.8°F) or higher, heat becomes a real risk and therefore matches must include cooling breaks. In a report by the World Weather Attribution, scientists stated weather conditions of 28°C (82.4°F) WBGT are dangerous for both players, fans, and workers, who are watching the games, attending fan festivals, and working inside and outside the stadiums. 

Fans attending the tournament this summer are also susceptible to serious heat illness as they may be less fit, older, may have pre-existing medical conditions, or may dehydrate themselves by drinking alcohol compared to the athletes, which can all contribute to higher risks of heat illness. 

How Can Host Cities Combat Extreme Heat

In light of these upcoming events, and continued rising average temperatures, more cities are dealing with an increased rate of projected extreme heat days and worsening heat waves. To address this, the Community Data Health Initiative (CDHI)’s Extreme Heat Learning Cohort hosted its quarterly virtual call in April featuring guest speaker Dr. David W. DeGroot, an expert in cold and heat stress physiology. 

Dr. DeGroot, the director of the Army Heat Center at the Martin Army Community Hospital in Fort Benning, Georgia, spoke to the cohort about low tech, budget-friendly strategies for cooling body temperatures based on his research expertise and work with the Warrior Heat-and Exertion-Related Events Collaborative. For many cities, these insights apply to outdoor workers, who “are at risk for heat-related illnesses and injuries” due to unique work conditions including “intense physical labor, protective gear, and the urban heat island effect.” This year, cities hosting FIFA games can also draw from this information to mitigate the risks of extreme heat for fans and stadium workers.

Arm Immersion Cooling

“When we developed arm immersion cooling back in 2008, we had three criteria,” explained Dr. DeGroot of its use for troops stationed in climates of extreme heat. “One: it needs to be effective, not just in reducing core temperature, but also reduce risk of becoming a heat casualty. Two: it needs to be simple. Logistically, in locations where we train infantry and rangers, we're out in the field and away from power sources. And three: it needs to be portable.”

Cold water is a much more effective medium than air to pull heat away from the body, so Dr. DeGroot and his colleagues wanted to take advantage of that, he explained. “When we consider just the surface area of just our hands and our forearms – basically up to the elbow immersion – that's about 10% of what's our body's skin surface area,” said Dr. DeGroot. “And by putting your arms in that cold water, we can augment heat loss.”

Through mining existing data from the Ranger School at Fort Benning, Dr. DeGroot was able to show that research proves that arm immersion cooling reduces the frequency and severity of heat illness. Dr. DeGroot also explained that executing arm immersion cooling requires no standard equipment because it is essentially a bucket or container of cold water large enough to submerge one's forearms.

“As simple as filling the kitchen sink with cold water, or using your bathtub. You don't need to go buy something,” emphasized Dr. DeGroot. “You have tap water, and if you've got a fridge with an ice maker, you're all set. You have everything you need to replicate this.” For city leaders looking to affordably protect residents, workers, and visitors in extreme heat seasons, arm immersion cooling is an easy way to do so without breaking the bank. 

The goal is to reduce the core body temperature, Dr. DeGroot explained. So while the container the water is in can be interchangeable, the most important factors of this cooling technique is the temperature of the water and the duration of arm immersion cooling. Using near-freezing water with an immersion duration of three to five minutes is needed to reduce core body temperature by one degree Fahrenheit. Less immersion time can still be beneficial, but less so.

Fans

For cities with humid climates, including along the east coast and in Southern states, fans are an effective tool to help facilitate evaporative heat loss, or sweat evaporating off of our skin. In these climates, sweat gathers on the skin’s surface but high humidity prevents it from evaporating from our skin – otherwise known as latent heat of vaporization. 

“Sweat hasn't done a darn thing to keep us cool until that sweat evaporates, pulling heat away from the skin,” said Dr. DeGroot. “The evaporation of one liter of sweat takes with it 680 calories worth of heat, but it has to evaporate. Sweat that just drips off of us, doesn't help keep us cool. Sweat that's trapped in our clothing or wiped away by a towel does not keep us cool. It has to evaporate from the skin's surface, and that's where fans help by increasing air movement across the skin.”

Misting

For cities that experience dry heat climates, largely in the western and southwestern states in the U.S., misting can be an effective tool for heat loss augmentation. In those dry climates where sweat is less able to accumulate on skin, especially in older individuals who have a lower sweat rate, adding moisture to the skin by misting allows for the evaporation process on the skin to occur. 

“The source of the moisture on the skin surface doesn't really matter whether it's coming from a sweat gland or a spray bottle. If it's evaporating, it's taking heat with it,” explained Dr. DeGroot. “So if my sweat rate's not enough [to cool the body], I can augment that with some moisture on my skin in an environment where it can freely evaporate – a drier environment like the desert southwest.”

Which Cooling Strategies Work for Your City’s Climate

With increasing average temperatures across the U.S., Dr. DeGroot emphasized that using more than one of these low tech cooling strategies is not necessarily beneficial. While arm immersion cooling works under any hot climate conditions, fans are ineffective in extreme dry heat climates and misting is ineffective in humid environments — and can exacerbate thermal stress and heat illness symptoms. Furthermore, the use of fans and misting together can cancel out each other’s cooling benefits.

Keeping in mind the variety of heat climates across the U.S., Dr. DeGroot explained it's best to facilitate the cooling strategy specific to your local summer heat conditions. For example, Vancouver is adding misting stations and drinking fountains, and in Dallas, local medical professionals will be equipped with ice and ice immersion bags. 

For FIFA World Cup host cities this summer – or any city hosting outdoor public events in the summer months – these affordable, low tech cooling strategies are accessible and uncomplicated ways to reduce serious heat illness and help protect residents, visitors, and outdoor workers from the effects of extreme heat due to climate change.