Arctic weather has begun arriving in Britain, with temperatures plunging as low as minus 7C overnight in areas of Scotland and northern England.
County Durham in the snow (reader photo: Colin Blackburn)
Motorists have been warned to take extra care after snow fell in Scotland and eastern England. Parts of Norfolk and Suffolk also received a dusting.
Everywhere is expected to feel very cold on Tuesday with temperatures in England and Wales reaching 3C at best.
But many areas are predicted to fall to minus 15C on Wednesday with windchill.
The Met Office has issued an advance weather warning for much of the UK, with severe weather expected to cause widespread disruption.
A BBC weather spokeswoman said: "The harsh weather is expected to spread south as the week continues, with few areas likely to escape the wintry conditions."
One person died and at least 10 others were taken to hospital following a crash between two coaches in icy weather conditions in East Yorkshire on Tuesday morning.
Czech and Portuguese nationals being taken to work were among passengers involved when the vehicles collided around at Tibthorpe near Driffield.
The dead man was one of the coach drivers.
Nick Grainger from Humberside fire and rescue said road conditions were "truly treacherous with black ice" and were likely to have contributed to the accident.
Twenty three schools in north-east Scotland have been either closed or partially shut as a precaution amid fears the area could be hit by heavy snow.
The Shetland Islands has had two inches of snow in some parts of the islands and high winds are causing some drifting.
The Highways Agency is urging drivers to check the weather forecast before they set off and to listen to radio bulletins while they are on the road.
Staff Britain's salt mines are working overtime to produce thousands of tonnes of grit as the nation prepares for the long-threatened big freeze.
Winsford Rock Salt Mine, in Cheshire, is supplying natural rock salt to hundreds of Highways Agency gritters in a bid to ensure roads remain thawed.
The agency has 700 gritters and snow-blowers ready to ensure there is no repeat of last year's winter roads chaos, when much of the country ground to a halt in icy weather.
It was criticised last year after thousands of drivers were trapped by snow on the M11 and M25, but says it is ready for action.
Snow and high winds elsewhere in the world hit hundreds of airline passengers, with flights to and from Britain cancelled.
British Airways cancelled 20 flights, all from Heathrow and Gatwick, including two flights to Glasgow.