Heavy snowfall and icy storms are set to leave much of the country shivering during the next few days.
Snow has already started to fall in parts of Wales, and is expected to hit the South West before pushing across the rest of the UK.
But forecasters are predicting the heaviest snowfall of the winter will come on Friday
Up to 10 inches of snow is expected to fall on higher ground, and between three and five inches on lower ground.
Train services are expected to be cancelled, and airports and schools to close.
Temperatures are expected to remain below zero in most parts, making it bitterly cold, while blizzards and strong winds are set to make conditions treacherous on the roads.
Motorists are being warned that heavy snow will arrive before the morning rush-hour.
The Met Office has issued severe weather warnings for the East Midlands, North West and South West England, Wales, the West Midlands and Yorkshire & Humber.
It comes after a bitterly cold night for much of the UK on Wednesday, with temperatures over East Anglia dropping to -11C.
Further snow showers are expected on Saturday, particularly along eastern coastal areas, with lighter snow showers on Sunday in the Midlands and northwards.
Sky News weather presenter, Jo Wheeler, said: "Temperatures will drop, fog will thicken in the east and there'll be a widespread frost.
"As the rain spreads across Wales and the South West, it will give significant snowfall, potentially up to 9ins (25cm) over exposed uplands.
"There'll also be strong winds, with gusts of between 50mph and 60mph which will give blizzard conditions for a while.
"All in all, the travel situation will be quite atrocious for tomorrow's commute or school run.
"The snow will push eastwards during the day, and is expected to reach London around the middle of the day, and eastern coasts by evening.
"Behind the snow however, it will become milder, with rain showers following onto western coasts."
The Highways Agency has warned motorists to check forecasts, allow extra time for their journeys and avoid any unnecessary travel.
Steve Crosthwaite, head of the agency's national traffic operations centre, said: "During periods of severe weather we also suggest people consider whether their journey is essential. They may want to delay their travel until conditions improve."
Those who decided to travel have been urged to travel prepared with a fully charged mobile phone, warm waterproof clothes, boots and a blanket, some food and drink, and have a torch, ice scraper, de-icer and a shovel.
The freezing weather has already caused havoc on the roads, with the AA reporting about 1,000 breakdowns an hour, while the RAC said call-outs were up 35% to 10,000.
Rail passengers have been advised to check services before travelling.
South West Trains said it would be operating a revised timetable on a number of routes on Friday - including London to Bournemouth and Weymouth, London to Salisbury and Portsmouth, and London to Reading.
East Coast Trains is lifting ticket restrictions for all journeys on its trains which arrive in, or depart from, King's Cross station in London after 10am on Friday.
A spokesman for Southeastern Trains warned "there may be disruption on some routes through the day".
London Fire Brigade has also urged caution during the "Arctic blast".
It follows the rescue of an elderly man from a serious blaze in Wembley, north London, which is believed to have been caused by a halogen heater being placed too close to flammable items.
Firefighters were also called to a fire in Fulham, west London, after an electric blanket was left on for the weekend.
British Gas said it was expecting a "huge spike of activity" for its home service engineers this weekend, predicting they would attend around 20,000 call-outs.
In Norfolk, 93 schools have been closed due to the weather.