Swathes of Britain are on alert for up to four inches of snow as bitter winds from the North Pole push temperatures below -10C (14F) – colder than Iceland, Norway and Sweden.
Experts are warning to brace for harsh frosts and bitter Arctic gales to bring the coldest spell of winter so far.
It follows an unseasonably mild weekend which saw the mercury hit double figures as mild winds flowed in from the Atlantic.
We could see the coldest day of winter on Friday
The Met Office warned to brace for a “big change in the weather” after a relatively calm and settled start to the New Year.
Forecaster Marco Petagna said: “We could see the coldest day of winter on Friday.
“A cold front moving in from the Atlantic will bring heavy frost and frequent snowstorms.
“Daytime temperatures on Wednesday will be around four to six degrees C (39 to 43 F) but harsh winds will make it feel as if temperatures are well below freezing.
“Temperatures will become increasingly colder throughout the week and by Friday it is likely that nighttime temperatures will be as low as minus 2C (28F).”
Up to four inches of snow are expected to fall on parts of Britain
He said: “People will need to keep tuned to forecast updates because it is extremely likely that travel warnings will be issued.
“The frost is likely to harden which could give rise to a number of hazards.”
James Madden, forecaster for Exacta Weather, warned not to be lulled into a false sense of security by the mild start to the week.
He said Scotland and northern England are first in line for the cold before winer grips the entire country at the weekend.
“These conditions will be accompanied by widespread snow showers across most and if not all parts of the country.
“The first belt of snow is likely to hit northern and western parts of the country from Wednesday evening and during the early hours of Thursday.
“This will then spread to parts of The Midlands and central and southern England later; anywhere in the country could see snow into next weekend.”
A rapid change of weather mid-week will hit the country
Bitter winds could push thermometers as low as -14C (6.8F) overnight in northern regions next weekend with lows of -7C (19.4F) in central England and -2C (28.4F) in the south.
The mercury will struggle to get much above -5C (23F) during the day in the north while the south languishes close to freezing.
Bookies have seen a rush on people betting on the cold since wintry forecasts started to emerge over the past few days.
Coral is offering 8-1 from 12-1 on winter turning out to be the coldest ever while Ladbrokes is going 33-1 from 50-1 on the UK record low temperature of -27.2C (-16.96F) toppling.
The heaviest snowfall is expected in northern parts of Scotland
Coral’s Nicola McGeady. added: “It looks like snow could be heading our way and punters were quick to react by backing this winter to be the coldest on record.”
AccuWeather forecaster Eric Leister said although mild, Britain faces a wet and windy start to the week.
He said: “This change to milder weather will continue on Monday as a storm arrives from the Atlantic, causing rain and wind to spread from north to south.
“An unsettled weather pattern will prevail for much of the coming week with numerous Atlantic storms crossing the Isles.”