What is the maximum ambient temperature that humans can withstand?

Summer means warmer weather which for those in northern climes is generally welcome as a relief from the frigid temperatures that winter polar vortexes can bring. However, in recent years those cold spells almost seem the relief when compared to the sweltering heat that is becoming more and more common.

Since the 1960s, according to the US Environmental Protection Agency, the frequency of heatwaves has steadily increased and so too their length and intensity. From an average of two heatwaves per year sixty years ago Americans now have to deal with six.

Back when the United States was racing to get to the Moon for the first time, the mercury would register 2 degrees above the 85th percentile threshold across 50 cities during hot spells. Today it’s 2.3 degrees. As well, each spell of excessive heat is a day longer lasting roughly four days on average.

And perhaps more importantly, the heatwave season is 49 days longer than when Kennedy and Johnson were in the White House. Why should that be important? While people can acclimatize to high temperatures to a degree, with heatwaves hitting earlier and later than expected, they get caught off-guard and have greater exposure to the health risks associated with extreme heat.

High temperatures can lead to “heat stroke, heat cramps, heat exhaustion, dehydration and death,” according to the Centers for Disease Control and Prevention. Those aliments can affect anyone but some groups are more vulnerable like “pregnant women, people with heart or lung conditions, young children, older adults, athletes and outdoor workers.”

On average over 700 people in the US die from heat-related deaths, but blistering heatwaves can take a much more severe toll. A new study in Nature Medicine found that over 60,000 people in Europe died in 2022 because of the extreme heat last summer.

What is the maximum ambient temperature that humans can withstand?

The tolerances of every human body is different and so too the conditions under which they are exposed to high temperatures. The key to withstanding extreme heat is your body’s ability to sweat. This is one of the reasons that even when the temperature is in excess of your bodies temperature you can tolerate the heat, for a while.

This natural cooling mechanism works better the drier the air is because the more humidity, or water vapor, in the air limits the evaporation rate. In order to measure just how much heat the body can take, scientists look at the heat index, which accounts for both heat and humidity to give an idea of how the weather feels.

This gauge is also referred to as the wet-bulb temperature, what a thermometer would read if a wet cloth were wrapped around it. According to Zach Schlader, a physiologist at Indiana University Bloomington, a wet-bulb temperature of around 95º F, or 35º C, is pretty much the absolute limit of human tolerance.

Once the temperature has surpassed that, the process whereby your body gets rid of heat loses its efficiency to maintain its core temperature effectively. You won’t die on the spot but the adverse effects of high temperatures will begin to cause damage to brain and organs in the absence of being able to cool down quickly.

How long can humans survive extreme heat?

This is a tricky question and not something to be trifled with. Human core body temperature is roughly 98º F (37º C) and an increase of around 7 degrees could cause hyperthermia (overheating), collapse and coma, said John Brewer, professor of sport at the University of Bedfordshire, speaking to the BBC.

While hard scientific data on the maximum limits is hard to find, one competition that was canceled after one of the competitors died can give an idea, but is a cautionary tale. 2010 was the twelfth and last year of the World Sauna Championships in Finland.

Russian competitor Vladimir Ladyzhensky collapsed after six minutes in a 230 ºF (110 ºC) sauna and later died at hospital. Timo Kaukon, five-time champion who was also in the sauna, collapsed as well but survived. In 2003, the Finn managed to last 16 minutes in a sauna at the same temperature.

Most people that bathe in saunas keep the thermostat at 176º F (80º C) and only stay in for five to six minutes after which they will cool off rapidly with a “shower, or jump into a lake or the sea,” according to Finnish Sauna Society chief executive Kristian Miettinen.

However, the self-described “sauna freak” says that some prefer to turn the dial up to 266º F (130º C) or even 284º F (140º C) and only stay in for 3 or 4 minutes. Miettinen expressed surprise that Ladyzhensky died when there are people who have safely enjoyed saunas at 320º F (160º C).