UK weather: Snow, ice and freezing rain forecast as Met Office issues warning

Not all water freezes at zero degrees Celsius.

Water droplets can exist as liquid in clouds, even when the temperature is a few degrees below freezing – we call it ‘supercooled’ water.

It is only when the droplet comes into contact with something like a microscopic speck of dust, pollen or pollutant – known as a cloud condensation nuclei – that it will then freeze instantly around it.

Snow then starts to fall out of the cloud but as it gets closer to the ground, the air gets warmer until it reaches a layer that will be above freezing.

The snow then melts into rain, which most of the time in the UK, is what we end up experiencing.

However, under certain meteorological situations, there can be shallow layer of air near to the surface that is actually below freezing.

This layer is normally too thin for the water droplets to freeze back into sleet or snow but they are supercooled once again.

Consequently, as they are close to the ground – which is also below zero – the next time they hit a surface the droplet will freeze creating a layer of ice.