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

10th February 2011
If our body is about 37°C, why does 30°C feel so hot?

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.