What is wind chill factor, how is it calculated and what does it mean for UK weather?
Have you ever noticed it feels much colder than it was predicted on the weather forecast? Well here's why.
THE UK is facing freezing temperatures and icy conditions in the coming weeks.
While temperatures look set to plummet to -16C, icy winds can actually make the the temperature feel even colder. Here's why...
What is the wind chill factor?
The Met Office describes wind chill as the "feels like temperature" and if you experience it you will agree.
So for example, say the temperature is 3C, a particularly cold and powerful wind can make it feel like -2C.
In spring last year, parts of the UK began the day with temperatures of around 1C but the wind chill in some areas meant it felt like -5C.
How is it calculated and what does it mean?
There's still no universally agreed formula for wind chill.
It is not an exact science and depends on what you want to measure.
But the one used by Canada, the US and the Netherlands, is becoming the international standard.
And the Met Office uses it.
Environment Canada provides a rough guide to working out wind chill.
For instance, 0C will feel like -5C in a 12.4mph wind and -8C in a 31mph wind.
The calculation takes into account wind speeds and humidity to assess how the human body actually feels temperature
What is the dangerous wind chill factor level?
The spectre of frostbit increases when wind chill values fall below -27C.
Hypothermia can also set in at this point if you are not protected enough from the blasts/
On a calm day, our bodies insulate us with a boundary layer which warms the air closest to the skin.
But if it is windy, the wind will take the boundary layer away and the skin temperature will drop making us feel colder.