Britain woke up to temperatures of just -6C (21F) today as parts of the country faced hard frosts and freezing fog.

Forecasters say the cold snap could last for at least a week, with snow possible even at low levels as far south as the Peak District – and daytime highs only expected to get up to 7C (45F) today in southern areas.

The change in conditions after an unseasonably mild New Year’s Day has been brought about by a shift in an area of high pressure over northern France, bringing polar air, leading to mostly bright days and very cold nights.

An overnight low of -6C (21F) was recorded at both Glasgow and Braemar in Aberdeenshire shortly after 6am today – far below the UK low on New Year’s Eve night, which was 0.4C (32F) in Kielder, Northumberland.

And forecasters have warned Britain could face another Beast from the East within a fortnight following an atmospheric event known as Sudden Stratospheric Warming (SSW) that has happened over the last week.

Today, the mercury is not expected to climb far above 0C (32F) throughout the day in many areas of Britain

This is where the temperature suddenly rises high up in the stratosphere, between six and 30 miles above the North Pole, and it can result in a chain reaction that leads to very cold conditions from eastern Europe and Russia.

Today, the mercury is not expected to climb far above 0C (32F) throughout the day in many areas and is due to remain in single figures celsius across the country.

Met Office forecaster Emma Smith said: ‘It’s going to be a pretty cold start to the day – temperatures were down to minus six in Scotland and there has been a quite widespread frost.”

‘It’s dry out there so there won’t be a problem on the roads – there’s not much moisture around so obviously not much ice around.