An area of high pressure accumulating over Scandinavia is now pulling up very cold air from Eastern Europe and as far as Siberia.
By Monday, they predict daytime temperatures around 2° although add it could feel like -7°! Central overnight temperatures could drop to -6C and it will be colder still from Tuesday with more concentrated snow showers and a reasonable accumulation of snow.
The Siberian blast, blowing its way across the continent from Russian Federation, will bring snow storms and freezing weather to the eastern side of England and Scotland in the coming days.
The Met Office has issued the level two warning for many areas of the country, including the east of England.
Bright weather earlier this week led people to flock to the beaches in south Wales, despite the low temperatures.
'Last week we saw that take place - a sudden jump of around 50C - so that can disturb the way that cold pool of air moves around the North Pole very high up.
He added: 'There is a very big, very cold pool of air that circulates around the North Pole - sudden stratospheric warming, as it says on the tin, is when the stratosphere suddenly warms.
Its latest forecast says that temperatures could fall to -6 degrees below freezing and rising to just above zero during the day. "It will feel bitterly cold, there will be penetrating frosts, and snow may continue to cause problems all week".
"However, as the high drifts east to be over Scandinavia by the weekend, it will allow colder air from Eastern Europe to be drawn towards us".
Starting this weekend, Britain will experience the longest prolonged spell of cold weather since 2013, Met Office forecasters have warned.