What is the wind chill factor?

Discover why it feels so much colder on windy days, even if the air temperature hasn’t actually decreased

(Image source: Pixabay/Free-photo)

The wind chill factor is the temperature that a person feels due to the wind. This is different to the air temperature, and many weather forecasts distinguish between the two by stating what the actual temperature is, as well as the ‘feels like’ temperature.

A breeze can make it feel colder than it actually is, because when air circulates and blows across our skin, heat is lost from our bodies by evaporative cooling. The faster the wind speed, the greater this effect. The wind chill factor expresses the rate at which heat is lost from our exposed skin.

The process:

(Illustration by Nick Sellers/ The Art Agency)

1- Strong winds

If the wind is very strong then the body will become colder much faster.

2- Dilation

In a warm environment, our blood vessels dilate, allowing more heat to be lost to the air.

3- Moisture loss

In warm weather, the evaporation of sweat helps keep us cool, but breezes in cold weather can also increase the rate at which moisture evaporates.

4- Constriction

In a cold environment, our blood vessels constrict, limiting heat loss to the air.

5- The cooling process

As the wind brings cold air in contact with the skin, moisture evaporates and body heat is lost.

This article was originally published in How It Works issue 96

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