If Our Body Temperature Is 37 Degrees Celsius, Why Do We Feel Hot When It’s 37 Degrees Outside?

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If your body and its surroundings are at the same temperature, there is no temperature difference, which prevents heat transfer between these two entities. Your body is, therefore, unable to get rid of the excess heat it produces which is why you feel hot at 37 degrees Celsius (98.6 degrees Fahrenheit).

Everyone says that the ‘optimum’ body temperature is 37 degrees Celsius (98.6 degrees Fahrenheit). But if the temperature of your surroundings is 37 degrees Celsius, most people will start to feel warm or even hot. Why does that happen?

Shouldn’t the ambient temperature of 37 degrees Celsius feel just right to your body? In fact, you may feel warm even at temperatures below 37 degrees Celsius. Why is that?

Your Body Produces Heat All The Time!

The human body is a complex machine; a number of biochemical processes occur in the body at any given time. It doesn’t matter whether you are sitting idle, working out, taking a walk, dancing, or reading this article, there are numerous internal processes in your body that never stop.

All physical and metabolic activities in your body produce heat, i.e., they are exothermic processes. Heat is an unavoidable byproduct of the work being done by millions of cells inside your body. With so much work being done all the time, it’s critical for the body to shed some of this ‘waste heat’. It accomplishes this by dumping heat to the surroundings by circulating blood near the surface of the skin, by exhaling warm and humidified air, and by the process of evaporation of sweat.

As a result, the body gets cooled down, maintaining its optimum 37 degrees Celsius and functioning efficiently. This, of course, depends on other factors as well, such as age, gender and how physically active the individual is.

It’s critically important that your body stays at its ideal temperature, i.e., 37 degrees Celsius (98.6 degrees Fahrenheit) because if it doesn’t, many bodily functions start to break down. The cells and the metabolic reaction that happen in them occur most efficiently at these temperatures. At high (or extremely low) internal body temperatures, chemicals in the body could begin to break apart, spelling disaster for the body.

Also Read: What Is An Endotherm?

Why Does 37 Degrees Celsius (98.6 Fahrenheit) Feel Hot?

If the ambient temperature is 98.6 degrees Fahrenheit (37 degrees Celsius), we start to feel hot because our bodies are not able to shed the heat they produce, as a result of metabolic activities (within the body), which makes us feel hot.

Note that the ambient temperature is NOT THE ONLY factor that determines how hot or a cold a person feels. Other factors, like, airflow, humidity level and their clothing also play a role.

Our body works best when the ambient temperature is around 70 degrees Fahrenheit (21 degrees Celsius) because at this temperature, there is a stable difference in the temperatures of the body and the surroundings. Once again, note that this range is not the ideal temperature range for everyone; it often varies from one person to another.

Consequently, heat transfer occurs as heat travels from a region of high energy (our body) to a region of low energy (our surroundings).

However, if both the body and its surroundings are at the same temperature, there is no temperature difference, which prevents heat transfer between these two entities.

The body is, therefore, unable to get rid of the excess energy it possesses (as a result of metabolic and physical activities), which is why it feels hot when the ambient temperature is 37 degrees Celsius.

Skin Temperature Is Lower Than Body Temperature

There’s one more thing—your skin temperature is lower than your body temperature. So, if the temperature of your surroundings is the same as your body temperature, then you’re going to feel warm anyway, because your skin would feel comfortable at a much lower temperature.

This leads to another interesting question…

Also Read: What Is “Feels Like” Temperature And How Is It Measured?

Why Is 37 Degrees (98.6 Degrees Fahrenheit) The Ideal Body Temperature?

Why can’t it be 35 degrees? Or 40? Why is exactly 37 degrees found to be the ideal body temperature?

The answer is, in short, that this is an optimum temperature to prevent nasty bacterial and fungal growth. Of course, it varies from one microorganism to another, as there are millions of them, but 98.6 degrees Fahrenheit (37 degrees Celsius) is relatively better and at the same time, physically comfortable.

Research shows that the number of fungal species that can thrive (and consequently infect) an animal declines by 6 percent for every 1 degree Celsius (1.8 degree Fahrenheit) rise in temperature.

This is the primary reason why cold-blooded animals like amphibians and reptiles are prone to thousands of fungal species, whereas only a few of them can harm humans and other warm-blooded animals.

Furthermore, the idea that “37 degrees Celsius is the ideal body temperature” was originated by Dr. Carl Wunderlich, a 19th-century German physician who analyzed over 25,000 patients and recorded his observations. While many of his observations have stood the test of time and his work has contributed significanctly to human understanding of body temperature, his definition of what’s the normal body temperature has been debunked.

Also Read: Do We Sleep Better In Cold Or Warm Rooms?

Is 37 Degree Celsius Really The Ideal Body Temperature?

Interestingly, the fact that ’37 degrees Celsius should be the ideal body temperature’ is now being challenged. There are a number of reasons behind that:

1. Women tend to have higher body temperatures than men. Also, younger people have higher body temperatures than older people. Thus, it is clear that the ‘ideal’ body temperature varies among individuals. Body temperature depends on each individual’s basal metabolic rate (BMR).

2. Normal body temperature varies throughout the course of a day, being at its peak during the day.

3. Human beings are generally getting cooler.

Basically, we might actually be heading towards a lower ideal body temperature, but that’s perfectly fine… we’ll get used to it.

For now, here’s your takeaway—the ideal body temperature is not 37 degrees Celsius (98.6 degrees Fahrenheit), but actually closer to 36.4 degrees Celsius (97.5 degrees Fahrenheit)!

Test your knowledge about body temperature!

Can you answer three questions based on the article you just read?

References (click to expand)
  1. Time to redefine normal body temperature? - Harvard Health. Harvard University
  2. How the Body Regulates Heat - Rush University Medical Center. Rush University Medical Center
  3. Bergman, A., & Casadevall, A. (2010, December 30). Mammalian Endothermy Optimally Restricts Fungi and Metabolic Costs. (F. Dromer, Ed.), mBio. American Society for Microbiology.
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About the Author

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spearheads the content and editorial wing of ScienceABC and manages its official Youtube channel. He’s a Harry Potter fan and tries, in vain, to use spells and charms (Accio! [insert object name]) in real life to get things done. He totally gets why JRR Tolkien would create, from scratch, a language spoken by elves, and tries to bring the same passion in everything he does. A big admirer of Richard Feynman and Nikola Tesla, he obsesses over how thoroughly science dictates every aspect of life… in this universe, at least.