BONE-CHILLING winds could bring a monster five inches of snow tomorrow.
Freezing flurries are forecast across the UK - even down to the south coast - as icy -11C gusts take hold.
But before the white stuff blankets Britain, those living in northern areas will have to endure "blustery, wintry showers" and coastal gales.
And after a mild day yesterday, it will feel particularly chilly, with average day-time temperatures of 2C in Scotland, 6C in Wales and Northern Ireland, and 7C in England.
Met Office forecasters warn the weather will get even colder overnight, with "driving" and "relentless" winds making it feel glacial.
It will be most piercing in west London and Hereford where the mercury will plunge to -2C, but winds of 30mph will make it feel a biting -11C, according to a wind chill calculator.
Snow and hail showers will batter northern Scotland before spreading to eastern coastal counties and northwest England.
WXCharts weather maps show up to five inches will fall in the Scottish Highlands, but snow could even fall as far south as Southampton.
The Met Office gave a more conservative prediction of just a few centimetres.
A spokesperson for the forecaster added: "It's going to be a lot colder today with showers turning wintry in the north.
"Patchy rain and snow will then affect some western and southern areas before more snow over the next few days. Only a few areas will be spared."
Overnight temperatures will hover around freezing further north, rising to highs of just 4C throughout the day.
It will be exceptionally crisp in central Scotland and the Midlands near Buxton and Hartington, Derbyshire, where it may not climb above zero all day.
The cold snap has sparked warnings for ice are for northern Scotland and eastern England today, extending to south west England and western Wales tomorrow.
"Icy stretches" are likely to develop with the risk of injury on roads, railways and pavements.
Met Office meteorologist Claire Nasir said: "Wednesday marks the beginning of meteorological winter, and in fact through the first few days of December we watch as colder air will be interspersed with milder conditions coming in from the west with rain pushing across that colder air and turning to snow on its leading edge.
"Towards the north there will be a widespread frost with the risk of ice, a cold start to the day on Thursday.
"And then all change through Thursday into Friday. A band of cloud and rain will turn to snow on its leading edge, particularly in the north over high grounds, but over lower levels for a time.
"Then we'll see more rain as head into the latter part of Friday and into the weekend, which looks wet and windy yet again, then turning colder yet again through the latter part of the weekend."
Netweather forecaster Nick Finnis added: "A much colder day for all on Thursday in a cold arctic northerly wind, temperatures struggling to reach 4-5C in the east, 6-8C in the west, but with a ridge of high pressure building in from the west bringing a mostly dry day with sunshine compensating for the cold wind.
"There will be wintry showers along eastern coasts throughout the day and across the far southwest at first.
"Then all change again Thursday night, as a spell of wet weather moves east of the Atlantic all across parts, rain most prolonged and heavy in the south and west this time, a spell of snow preceding the rain for a time across northern areas, perhaps to lower levels for a time but settling mostly over high ground.
"Rain, sleet and snow clearing east first thing Friday morning, then a mostly cloudy and milder day with a north-westerly breeze and a few showers in places, though some sunshine across the northeast."
Tomorrow will mark the second day of a four-day deep freeze which is expected to last until at least Saturday - but could extend to mid-December.
During this time, forecasters reckon the UK could see several more inches of snow, with the night-time mercury a bitter -6C.
The wintry weather comes after killer Storm Arwen caused chaos across the UK.
Scotland and northern England bore the brunt of the chilly snap, but those further south have seen some icy conditions.
Thousands of homes have been left without power following the "catastrophic damage" of the storm.
Many may been waiting until at least Friday to be reconnected - meaning they will have been living off grid for an entire week.
Graeme Keddie, of SSEN, said the storm had caused "devastation on parts of the network", particularly in Aberdeenshire, where 4,000 customers remain without power.
SSEN managing director Chris Burchell said: "The impact of Storm Arwen has caused catastrophic damage to the electricity network across the north-east of Scotland and is the most significant event we have ever had to deal with in the area in a generation.
"I would like to thank our customers who have shown great resilience, patience and understanding since the impact of Storm Arwen, and we fully recognise that urgency of the situation for those who continue to remain off supply.
"I would like to personally apologise to all customers who have been impacted and would like to reassure everyone still off supply that our teams are working extremely hard to reconnect them as soon as possible."
The "Arctic shot" has pushed bookies to slash the odds of a white Christmas, and this year going down as the coldest winter on record.