If our body is about 37°C, why does 30°C feel so hot? © Getty Images

If our body is about 37°C, why does 30°C feel so hot?

When the surrounding air is the same temperature as our core body temperature our normal heat exchange processes just don't cut it.

Asked by: Rosie Day, Uttoxeter


Not all of your body is at 37°C – that’s just the temperature of your core. Your skin is much cooler than that because it’s continually exchanging heat with your surroundings. This is important because the energy released as a by-product of the chemical reactions in your cells would destroy them if it wasn’t continually dissipated. When the ambient temperature is 30°C, the temperature gradient between your core and your skin is shallower, so convection and radiation aren’t enough to dissipate heat as fast as it is generated. To compensate, you need to sweat (which removes heat through evaporation), fan yourself (forced convection) or have a cold drink. ‘Feeling hot’ is the warning light that your body uses to tell you to do one of these things. It’s controlled by the hypothalamus in the brain, which measures the temperature of the blood in your core.


Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.