It depends on the humidity.
As climate change causes global temperatures to rise, extreme heat is becoming an increasing threat to health. So, what is the maximum temperature that people can tolerate?
The answer is simple: According to a 2020 study in the journal Science Advances, wet bulb temperatures are 35 degrees Celsius. The wet bulb temperature is different from the temperature reported by a local forecaster or favorite weather app you might see. Instead, the wet bulb temperature is measured by a thermometer covered with a water-soaked cloth, which takes into account both heat and humidity. The latter is important because the more water in the air, the harder it is for sweat to evaporate from the body, cooling the person down.
Colin Raymond, a postdoctoral researcher at NASA's Jet Propulsion Laboratory, said that if humidity is low but temperatures are high, and vice versa, wet bulb temperatures may not approach the tipping point of the human body. However, when both humidity and temperature are high, humidity gradually approaches dangerous levels. For example, when the temperature is 46.1 degrees Celsius and the relative humidity is 30%, the wet bulb temperature is only 30.5 degrees Celsius. However, when the temperature is 38.9 C and the relative humidity is 77%, the wet bulb temperature is about 35 C.
The reason people can't survive high temperatures and humidity is that they can no longer regulate their internal temperatures. Raymond told Life Science: "If the wet bulb temperature is higher than the human body temperature, you can still sweat, but you can't cool the body to the temperature physiologically required."
At this point, the body becomes hot – above 40 degrees Celsius. According to the National Institutes of Health, this can lead to symptoms such as tachy pulse, changes in mental status, lack of sweating, fainting, and coma.
However, a humid bulb temperature of 95 degrees Fahrenheit doesn't immediately lead to death: Raymond said that heat could take about 3 hours to recover. The exact time could not be determined, he said, but the study sought to estimate by dipping human participants into a hot water tank and moving them out when their body temperature began to rise uncontrollably. There is also no way to confirm that 95 degrees Fahrenheit is the temperature of the wet bulb that cannot survive: Raymond estimates that the true number is between 93.2 F and 97.7 F (34C to 36.5C).
Although no one can live in wet bulbs with temperatures above about 35 degrees, lower temperatures can also be fatal. Exercise and exposure to direct sunlight are more likely to overheat. Elderly people / people with certain health conditions, such as obesity; People who take antipsychotics also can't regulate their body temperature, so heat energy kills them more easily. That's why people sometimes die in heat that doesn't reach 35 degrees.
Raymond said: "Unfortunately, because climate change is already in trouble, even if we stop emitting greenhouse gases today, we will continue to heat up." "I think that in the foreseeable future, the places I mentioned will inevitably deal with this issue, and I hope that more places will not be included in the list."