Decoded | How much heat can human body tolerate (2024)

New Delhi,UPDATED: Jul 3, 2021 00:12 IST

Normal human body temperature is 98.6-degree Fahrenheit which corresponds to 37-degree Celsius. Anything above is called fever, which can lead to hyperthermia in a heat wave condition. It could be fatal.

It is commonly held that the maximum temperature at which humans can survive is 108.14-degree Fahrenheit or 42.3-degree Celsius.

A higher temperature may denature proteins and cause irreparable damage to brain. Simply put, the human body can turn into a scrambled egg.

But the temperature outside is far higher, isn’t it?

Yes. Temperature has soared very high in several parts of the world. North India too is facing heat wave. Monsoon is delayed and temperature is high particularly in Delhi, Haryana, Punjab, Rajasthan and western Uttar Pradesh.

According to the India Meteorological Department (IMD), Delhi has witnessed a temperature 7-degree Celsius higher than the normal.

• Good thing is that humans are warm-blooded mammals. This means that they are protected by a mechanism called homeostasis, a process through which human brain — part called hypothalamus — regulates body temperature to keep it in the survival range.
• Dilation of blood vessels, sweating and breathing through mouth or the urge to go out in open spaces for fresh air are ways through which hypothalamus regulates human body temperature.

If body regulates temperature, why worry?

It is not so simple. Except in the cases of some illnesses or infections, the human body temperature depends on a number of variables, such as outside temperature, humidity and oxygen supply.

• In a 1985 report, Nasa explained that human body is ordinarily built to perform between a temperature range of 4-35-degree Celsius.
• But, if humidity is lower than 50 per cent, the human body can sustain much hotter weather conditions. The equation is simple. The higher the humidity, hotter the body feels and requires more sweating to regulate the inside temperature.

Basically, the point is, there is a limit to which hypothalamus can regulate a human body's temperature.

• Loss of water in a hotter and more humid condition can lead to hyperthermia. It begins with heat exhaustion and stress. The person may feel weak, dizzy, nauseous and thirsty.
• Several electrolytes such as sodium and potassium are lost. These electrolytes are essential for the functioning of heart, nervous system and muscles.

This leads to the collapse of the body system, and is the very reason to worry about heat or heat wave.

What is heat wave?

Declaration of heat wave varies from country to country depending on their climatic conditions. In India, a combination of two parameters decides declaration of a heat wave.

• The outside temperature should be above 40 degree Celsius.
• The temperature on a given day should be 4.5 degree Celsius higher than the previous five days.

But if temperature crosses 45 degree Celsius, the IMD or its regional centre does not wait for the temperature gap to reach 4.5 degree Celsius.

Also See: See how US, Canada are coping with record-breaking heatwave

Similarly, if the temperature on a day is over 6.5-degree Celsius higher than the average temperature on the past four-five days, the IMD declares it a “severe” heat wave condition.

What are the highest recorded temperatures at which humans have survived?

There is a place in the US’s California, called the Furnace Creek Ranch, which holds the record for highest temperature measured ever on the earth.

advertisem*nt

• It is 56.7-degree Celsius or 134-degree Fahrenheit. It was recorded on July 10, 1913. The place was then called the Greenland Ranch. But its high temperatures gave it its new name.
• Furnace Creek Ranch officially became the hottest place on the earth after the World Meteorological Organisation (WMO) rejected the claim of 58-degree Celsius recorded at El Azizia in Libya in 1922 in a review during 2010-12.

In India, Phalodi in Rajasthan holds the record for highest temperature measured ever.

• Phalodi, near Pokharan, recorded the temperature of 51-degree Celsius or 123.8-degree Fahrenheit on May 19, 201.
• In Churu (Rajasthan), which often makes news for high temperatures, it reached 50.2-degree Celsius or 122.4-degree Fahrenheit in August 2017.

On June 10, 2019, Delhi recorded its all-time high temperature of 48-degree Celsius clouding the previous high of 47.8-degree Celsius that was recorded in Palam on June 10, 2014.

What is fuelling current phase of global heat waves?

Right now, many parts of the world are witnessing severe heat waves. Though each region has a unique set of factors fuelling heat waves, weather scientists believe the principal cause is climate change. It has triggered varied weather responses in different corners of the world.

advertisem*nt

• Canada and the US are facing one of the worst heat waves with many cities reporting all-time high temperatures.
• Washington DC measured 42.2-degree Celsius earlier this week which is the highest for the city since the US began keeping record of temperatures.
• In Canada, the temperature went up to 49.5 degree Celsius this week.

Weather scientists have attributed searing temperatures in the US and Canada to heat dome phenomenon.

This happens when ocean temperatures rise abnormally high and hot air moves towards land. In a heat dome situation, atmosphere of a place acts like a lid and traps hot air coming from the sea.