Early winter weather swept south overnight and is predicted to engulf the whole country in snow and subzero temperatures by tonight.
Up to 5.8cm (2in) fell in the Midlands, and flurries have reached London, while Scotland and the north-east faced new cold fronts advancing from Scandinavia.
Sixty cars were rescued from a snow-blocked slope near Louth, in Lincolnshire, on one of hundreds of roads put out of use by the snowfalls. Schools have given up the struggle to stay open in parts of Kent, East Anglia, the south-west and Wales, as well as across much of Scotland and the north-east.
Severe weather warnings were issued early today for the whole of the UK, bringing in areas of the north-west and the West Midlands that had escaped disruption. Snow is expected to reach up to 8cm in higher parts of the home counties.
Late last night, 100 commuters were stranded for two hours near West Malling, in Kent, after points froze. The 11.07pm service from London Victoria fell victim to the icy weather between Borough Green and West Malling and had to be towed to safety by another train.
Temperatures reached a low of -13C (55F) in Inverness this morning, with fresh north-easterly winds adding the new factor of wind chill. The AA predicted yesterday's tally of 20,000 breakdowns would be exceeded today. Edinburgh airport reopened this morning but warned of disruption; flights at most other airports are vulnerable to delays.
The chill is expected to last for the rest of the week, with a gradual rise in temperatures likely to bring more snow before rain takes over at, or shortly after, the weekend.
Wholesale electricity prices have risen by 34% and gas by 10%, taking them to their highest levels for 22 months and 21 months respectively.
Public spending faces a second tranche of cold-weather payments to nearly 4m households, cash triggered by records or forecasts of 0C temperatures for a week. Tiffany Curnick, of MeteoGroup forecasters, said the dominant easterly weather flow was continuing to stream in, bringing some further accumulations of snow.
The Met Office forecaster Tom Morgan said: "Temperatures today are going to be very cold, and we are looking at 1C to 2C, with a very strong north-easterly wind. In towns or cities, we're looking at -2C to -4C tonight, dropping to -6C or -8C in less sheltered parts. The cold spell is going to continue but will be less widespread as we go through the week."
Rail services have been delayed across the country, with buses replacing trains on some Southeastern services in Kent. There are also problems in Surrey and the north London suburbs, and the East Coast mainline and ScotRail are working to reduced timetables.
Separately, scientists in Alaska announced new discoveries about polar bear behaviour, including a previously unrecorded system of adults carrying cubs on their backs while swimming. The study suggests this may have developed because reductions in Arctic ice are forcing the bears to swim greater distances on their hunts for food.
