The Temperature the Human Body Cannot Survive

One recent case of extreme heat threatening health came at a jamboree in South Korea, where hundreds of scouts fell ill. ANTHONY WALLACE / AFP/File
One recent case of extreme heat threatening health came at a jamboree in South Korea, where hundreds of scouts fell ill. ANTHONY WALLACE / AFP/File
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The Temperature the Human Body Cannot Survive

One recent case of extreme heat threatening health came at a jamboree in South Korea, where hundreds of scouts fell ill. ANTHONY WALLACE / AFP/File
One recent case of extreme heat threatening health came at a jamboree in South Korea, where hundreds of scouts fell ill. ANTHONY WALLACE / AFP/File

Scientists have identified the maximum mix of heat and humidity a human body can survive.

Even a healthy young person will die after enduring six hours of 35-degree Celsius (95 Fahrenheit) warmth when coupled with 100 percent humidity, but new research shows that threshold could be significantly lower.

At this point sweat -- the body's main tool for bringing down its core temperature -- no longer evaporates off the skin, eventually leading to heatstroke, organ failure and death, said AFP.

This critical limit, which occurs at 35 degrees of what is known as "wet bulb temperature", has only been breached around a dozen times, mostly in South Asia and the Arabian Gulf, Colin Raymond of NASA's Jet Propulsion Laboratory told AFP.

None of those instances lasted more than two hours, meaning there have never been any "mass mortality events" linked to this limit of human survival, said Raymond, who led a major study on the subject.

But extreme heat does not need to be anywhere near that level to kill people, and everyone has a different threshold depending on their age, health and other social and economic factors, experts say.

For example, more than 61,000 people are estimated to have died due to the heat last summer in Europe, where there is rarely enough humidity to create dangerous wet bulb temperatures.

But as global temperatures rise -- last month was confirmed on Tuesday as the hottest in recorded history -- scientists warn that dangerous wet bulb events will also become more common.

The frequency of such events has at least doubled over the last 40 years, Raymond said, calling the increase a serious hazard of human-caused climate change.

Raymond's research projected that wet bulb temperatures will "regularly exceed" 35C at several points around the world in the coming decades if the world warms 2.5C degrees above pre industrial levels.

'Really, really dangerous'Though now mostly calculated using heat and humidity readings, wet bulb temperature was originally measured by putting a wet cloth over a thermometer and exposing it to the air.

This allowed it to measure how quickly the water evaporated off the cloth, representing sweat off of skin.

The theorized human survival limit of 35C wet bulb temperature represents 35C of dry heat as well as 100 percent humidity -- or 46C at 50 percent humidity.

To test this limit, researchers at Pennsylvania State University in the United States measured the core temperatures of young, healthy people inside a heat chamber.

They found that participants reached their "critical environmental limit" -- when their body could not stop their core temperature from continuing to rise -- at 30.6C wet bulb temperature, well below the previously theorized 35C.

The team estimated that it would take between five to seven hours before such conditions would reach "really, really dangerous core temperatures," Daniel Vecellio, who worked on the research, told AFP.

The most vulnerableJoy Monteiro, a researcher in India who last month published a study in Nature looking at wet bulb temperatures in South Asia, said that most deadly heat waves in the region were well below the 35C wet bulb threshold.

Any such limits on human endurance are "wildly different for different people," he told AFP.

"We don't live in a vacuum -- especially children," said Ayesha Kadir, a pediatrician in the UK and health advisor at Save the Children.

Small children are less able to regulate their body temperature, putting them at greater risk, she said.

Older people, who have fewer sweat glands, are the most vulnerable. Nearly 90 percent of the heat-related deaths in Europe last summer were among people aged over 65.

People who have to work outside in soaring temperatures are also more at risk.

Whether or not people can occasionally cool their bodies down -- for example in air conditioned spaces -- is also a major factor.

Monteiro pointed out that people without access to toilets often drink less water, leading to dehydration.

"Like a lot of impacts of climate change, it is the people who are least able to insulate themselves from these extremes who will be suffering the most," Raymond said.

His research has shown that El Nino weather phenomena have pushed up wet bulb temperatures in the past. The first El Nino event in four years is expected to peak towards the end of this year.

Wet bulb temperatures are also closely linked to ocean surface temperatures, Raymond said.

The world's oceans hit an all-time high temperature last month, beating the previous 2016 record, according to the European Union's climate observatory.



UK Farm Swaps Milk for Cow Cuddles

Visitor Jess Tinton embraces a cow during a "Cow Cuddling" experience at Dumble Farm in Arram, Britain, June 17, 2025. REUTERS/Phil Noble
Visitor Jess Tinton embraces a cow during a "Cow Cuddling" experience at Dumble Farm in Arram, Britain, June 17, 2025. REUTERS/Phil Noble
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UK Farm Swaps Milk for Cow Cuddles

Visitor Jess Tinton embraces a cow during a "Cow Cuddling" experience at Dumble Farm in Arram, Britain, June 17, 2025. REUTERS/Phil Noble
Visitor Jess Tinton embraces a cow during a "Cow Cuddling" experience at Dumble Farm in Arram, Britain, June 17, 2025. REUTERS/Phil Noble

Years of floods and low food prices have driven a dairy farm in England's northeast to stop milking its cows and instead charge visitors to cuddle them.

Dumble Farm started as a dairy farm in the 1970s, but in recent years flooding washed out crops and killed off the type of grass the cows like to eat, while milk prices below cost of production proved an insurmountable challenge, Reuters reported.

"The amount of flooding and the pressures on our land were just making it unsustainable for us to carry on," said Fiona Wilson, co-owner of the farm.

Agriculture is one of the sectors worst-affected by climate change, with farmers in Europe and elsewhere suffering under increasing heat, drought and flooding.

In 2022, Dumble Farm sold all but a few of its dairy cows and, in a scramble to reinvent itself, began offering "cow cuddling" experiences to fund a wildlife conservation scheme.

For 95 pounds ($127.80), visitors can cuddle, brush and stroke the cows as they lie down on a straw-covered enclosure inside a barn. The experience includes a safari to see Highland cattle.

"It's been so worth it, just to get so close to the cows, and they are so loving and gentle," guest Emma Hutton, 25, said after she spent some time cuddling one of the cows.

It took over a year to train the cows to feel comfortable with cuddling, but now the animals have fully adjusted, farmer James McCune said.

"They like being pampered. They are like big dogs... It's more of a spa day for the cows," McCune said. The farm uses the proceeds to create habitats to protect wildlife and support declining species, such as lapwing birds.

"It's great that we can fund the conservation scheme by having visitors to the farm, and that's really the bigger picture," Wilson said.