A cold snap will grip the country today - a bitter prelude to a weather system that will leave the UK covered in up to four inches of snow by the weekend.
Thermometers are set to plummet, with many parts of the country struggling to see temperatures rise above freezing.
Motorists will have to be wary as freezing fog that has formed overnight across the Midlands, East Anglia and central and southern England could make road conditions hazardous.
In Norfolk 262 schools have closed due to the weather.
The lowest temperatures overnight were -12.7C at Braemar in Scotland and -12.1C at Houghton Hall in Norfolk, according to MeteoGroup, the weather division of the Press Association.
Gemma Plumb, a forecaster with MeteoGroup, said it had been bitterly cold for much of the UK overnight - average temperatures were between -3C and -7C, and -3C in London - with worse to come.
"Most places are looking like they will be dry today, with some sunny spells around. But fog and low cloud could linger in places like the East Midlands and East Anglia, with further outbreaks of sleet and snow across parts of western Scotland," Ms Plumb said.
"But it is going to be very cold today, with many places struggling to see temperatures rising above freezing. Parts of Scotland, northern England, Wales, the Midlands and East Anglia will be looking at maximum temperatures of -1C or zero."
A weather front moving across the UK on Thursday night is set to bring the biggest snowfall of the winter. Ms Plumb said: "At the moment we are looking at 5cm to 10cm (2in-4in) falling quite widely across the country on Friday, with more than that locally, especially across higher ground."
Darron Burness, of the AA, said motorists should take measures to prepare for the cold weather and coming snow. "The main problem is flat or failed batteries, as the car's electrical system has to work much harder in the cold," he said. "When you get in your car, switch off all the electrics before starting it - for example, blowers, lights and heated windscreen - and dip the clutch while starting to take some of the load off the starter motor and, in turn, the battery."