A 400-mile wide 'Arctic swell' is expected to brings -9C temperatures tonight (Monday) - making it the coldest night in autumn.
And there's more bad weather news, as the UK is set to be hit by another round of flooding with two inches' of rain expected to fall on Tuesday.
The downpours comes after snowfall, which hit Bristol on Thursday - England's earliest flurry for 11 years.
Britain is currently colder than Helsinki, as polar air cools the country bringing -3C nights, and Monday is tipped to be the coldest of the autumn so far, reports the Mirror.
The Met Office has warned Scotland temperatures will sink lower than last week's -8.1C at Dalwhinnie, Highland.
While temperatures in England are expected to drop to a chilly -6C in the north.
Temperatures in the south of England are set to plummet to -3C, while the north is facing snow flurries on higher ground.
Bristol residents will escape the worst of the cold snap with the mercury only dropping to 2C overnight on Monday.
Met Office forecaster Greg Dewhurst said: "Slow-moving rain returns to the West on Tuesday and to Yorkshire and other parts from Thursday for the rest of the week, with bands of rain.
“It's cold in the northerly flow. Monday night could be the coldest night of autumn in Scotland and England, exceeding -8.1C in Scotland and down to -6C in northern England.
"Snow showers could be seen on higher ground of Scotland, with a bit of snow over northern England.
"Daytime maximums will be 7-9C for most to start the week, easing to 12C in the South from midweek as the flow turns southerly, but still only 7-10C in the North.
"It stays unsettled from next weekend onwards, with bands of rain through the following week.”
Following the snowfall, Coral has slashed white Christmas odds to 4/1 in Glasgow, 7/1 in Birmingham and 10/1 in London.
Spokesman for the gambling firm Harry Aitkenhead said: “The white stuff's already falling and so are the odds.”
Met Office weather forecast
Monday:
A dry day for many, with occasionally bright spells, though isolated showers are still likely to affect eastern coastal areas at times, breezy here also. Frosty in the west overnight. Maximum temperature 10 °C.
Outlook for Tuesday to Thursday:
Patchy rain over Kent at first on Tuesday, clearing east to leave a dry afternoon. Dry initially Wednesday, though patchy rain later. Breezy on Thursday with further rainfall at times.
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