Snow is expected to blanket the UK for the next week, with no end of the big freeze in immediate sight.
The prediction of prolonged cold weather will bring a further chill to commuters and holidaymakers after two days of snow brought airports and transport networks to a shuddering halt.
Large parts of the UK will experience further snowfall on Sunday, with up to 4cm falling in the West and North and 6cm in the East Midlands, East Anglia and the South East, including London. Up to 10cm could fall in local areas, and 15cm on higher ground, weather experts said.
The Met Office has issued yellow warnings for ice for much of the country and advised people to take extra care as snow turns to ice in the sub-zero conditions.
While thousands of passengers were stranded at Heathrow airport for a second day on Saturday amid grounded planes, four climbers were swept to their deaths in an avalanche in the Scottish Highlands. They were climbing on Bidean Nam Bian near Glencoe when a snow-covered slope is believed to have given way, sending them hundreds of feet to their deaths. Two of the six-strong party survived, one of whom, a woman, is seriously injured in hospital.
Seven people were also taken to hospital after a double-decker bus collided with two cars and ploughed into a garden, Humberside Fire and Rescue Service said.
London's Heathrow Airport is braced for another day of chaos as around 260 flights are to be cancelled - more than twice the number on Saturday, and 20% of the total number of departures. Following a joint decision by Heathrow, airlines and air traffic control, the flight schedule will be reduced in an effort to minimise the expected disruption caused by snow and low visibility.
Heathrow later announced its flight schedule on Monday will be reduced by 10%, about 130 flights.
Meanwhile, it emerged a teenager was critically injured in an accident while out sledging. The 16-year-old suffered "life-threatening" head injuries after falling off a toboggan at speed in Middlesbrough. He was airlifted to hospital and is said to be fighting for his life.
A Great North Air Ambulance spokesman said crews were called to land near Flatts Lane Country Park at 1.25pm on Sunday. The spokesman described the boy's injuries as life-threatening, adding: "He was given an anaesthetic at scene before being transported to the James Cook University Hospital in Middlesbrough in a critical condition."