Met Office issues weather warning as freezing fog to sweep across South West

The Met Office has issued a weather warning as freezing fog is due to sweep across parts of the South West this weekend.

The warning is in place from 2am on Saturday (21 January) until 11am the same day.

The changing weather is likely to bring travel disruption, slower journey times and delays to bus and train services. There is also a chance that flights will be delayed or cancelled.

The forecaster said: "Some fog should be quite dense with the visibility falling below 100 metres at times.

"Additionally, freezing fog may lead to some untreated surfaces becoming slippery.

"Western England is more likely to see freezing fog persist into late morning and in a few places into the afternoon."

What is freezing fog?

The Met Office explains that freezing fog forms in the same way as normal fog, when the land cools overnight under clear skies. The heat then radiates back into space leading to the cooling of surfaces.

This means the air is less able to hold moisture which allows water vapour to condense into tiny water droplets and eventually lead to the formation of fog.

When these droplets freeze, a white deposit of feathery ice crystals is formed. This is referred to as rime - a characteristic of freezing fog which is often seen on vertical surfaces exposed to wind.

We tend to get freezing fog during the winter when temperatures drop below freezing and there are clear skies and calm conditions.