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.



SpaceX Starship Explodes During Routine Test

Flames rise as a SpaceX rocket explodes in Brownsville, Texas, US, June 18, 2025, in this screengrab obtained from a social media video. TheRocketFuture via X/via REUTERS
Flames rise as a SpaceX rocket explodes in Brownsville, Texas, US, June 18, 2025, in this screengrab obtained from a social media video. TheRocketFuture via X/via REUTERS
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SpaceX Starship Explodes During Routine Test

Flames rise as a SpaceX rocket explodes in Brownsville, Texas, US, June 18, 2025, in this screengrab obtained from a social media video. TheRocketFuture via X/via REUTERS
Flames rise as a SpaceX rocket explodes in Brownsville, Texas, US, June 18, 2025, in this screengrab obtained from a social media video. TheRocketFuture via X/via REUTERS

One of Elon Musk's SpaceX Starships exploded during a routine test late Wednesday in Texas, law enforcement said, in the latest setback to the billionaire's dream of turning humanity into an interplanetary species.

The Starship 36 suffered "catastrophic failure and exploded" at the Starbase launch facility shortly after 11:00 pm (0400 GMT Thursday), a Facebook post by the Cameron County authorities said, according to AFP.

A video shared with the post showed the megarocket attached to the launch arm, and then a flash and a towering, fiery explosion.

Musk's Space X said the rocket was preparing for the tenth flight test when it "experienced a major anomaly while on a test stand at Starbase," without elaborating on the nature of the complication.

"A safety clear area around the site was maintained throughout the operation and all personnel are safe and accounted for," Space X added on social media.

"There are no hazards to residents in surrounding communities, and we ask that individuals do not attempt to approach the area while safing operations continue."

The Starship was not scheduled for launch on Wednesday evening when the explosion occurred during a "routine static fire test," according to the Cameron County authorities.

During a static fire, part of the procedures preceding a launch, the Starship's Super Heavy booster would be anchored to the ground to prevent it from lifting off during the test-firing.

Starbase on the south Texas coast, near the border with Mexico, is the headquarters for Musk's space project.

Standing 403 feet (123 meters) tall, Starship is the world's largest and most powerful rocket and central to Musk's long-term vision of colonizing Mars.

The Starship is billed as a fully reusable rocket with a payload capacity of up to 150 metric tons.

The latest setback follows an explosion of a prototype Starship over the Indian Ocean in late May.

The biggest and most powerful launch vehicle ever built had lifted off on May 27 from the Starbase facility, but the first-stage Super Heavy booster blew up instead of executing its planned splashdown in the Gulf of Mexico.

The previous two outings also ended poorly, with the upper stage disintegrating over the Caribbean.

But the failures will likely do little to dent Musk's spacefaring ambitions.

SpaceX has been betting that its "fail fast, learn fast" ethos, which has helped it dominate commercial spaceflight, will eventually pay off.

The company has caught the Super Heavy booster in the launch tower's giant robotic arms three times -- a daring engineering feat it sees as key to rapid reusability and slashing costs.

NASA is also increasingly reliant on SpaceX, whose Dragon spacecraft is vital for ferrying astronauts to and from the International Space Station.

The Federal Aviation Administration (FAA) in early May approved an increase in annual Starship rocket launches from five to 25, stating that the increased frequency would not adversely impact the environment.

The decision overruled objections from conservation groups who had warned the expansion could endanger sea turtles and shorebirds.