How Wind, Rain and Sweating Make You Colder
It seems fairly obvious that wind makes you cooler. Just think of a fan on a hot day. But what is actually happening?
When our skin is in contact with colder air, the air very near the skin and the skin itself reach an equilibrium that’s warmer than the air and cooler than the skin.
But our bodies lose heat through evaporation, convection, conduction, and even radiation, so when the wind blows on our skin it pulls with it the warmer air near the skin and even pulls some of the heat out of the skin itself, making us feel colder.
When your warm skin touches a cooler object or garment, heat is transferred from your body.
“The better the material is at conductivity, the more the heat will transfer. When you touch a piece of wood and metal and both are below your skin temperature, the metal feels colder because it conducts more heat,” says Dr Greg Haggquist, a research scientist who founded fabric technology company 37.5.
So it’s important to have materials with low conductivity against the skin, like wool.
Your body loses heat to the air. Air blows away from the skin, new air replaces it, grabs some heat and blows away again.
“We can play with convection by changing the air permeability of fabric. If we have a fabric that allows lots of airflow, like a mesh, then convective heat loss will be increased,” says Haggquist.
When perspiration evaporates, it takes heat with it. This is the body’s method of cooling itself.
Just like heat from a woodstove, warmth radiates from the body. We lose around 65% of body heat through radiation in air temperatures lower than 68°F/20°C.