Freezing conditions are continuing to affect parts of the UK, as forecasters warn it could be facing the coldest night of the year.
A fourth day of wintry weather has caused widespread disruption, affecting flights, trains and ferries.
Yellow Met Office warnings for snow and ice have been extended until 11:00 GMT on Tuesday. Forecasters are predicting temperatures could hit -15C (5F).
Hundreds of schools are to stay closed for a second successive day on Tuesday.
The Met Office's weather warning covers Wales, Northern Ireland, parts of Scotland, the Midlands, London and the South East of England.
Clear skies overnight could lead temperatures to drop lowest in Wales and central England.
A low of -11.6C (11F) was recorded on Sunday night in Chillingham Barns, Northumberland, although Saturday was the coldest night of the year so far, reaching -12.4C.
BBC weather forecaster Steve Cleaton said hazardous conditions would continue in the coming days, although there would be less snow than at the weekend.
"A perishingly cold night is expected as we move through Monday evening into Tuesday, with another widespread and severe frost, and temperatures plummeting to below -10C across any snowfields," he said.
Over 350 schools in the West Midlands are to close for another day, while in Wales about 180 schools so far have said they will shut.
More than 1,000 schools didn't open on Monday - nearly 600 of those were in Wales.
Wintry conditions have caused significant disruption for travellers:
- Chiltern Railways, Arriva Trains Wales, Cross Country, East Midlands Trains, Great Western Railway, Thameslink, Virgin Trains and the West Midlands rail network were all affected - National Rail says travellers should check with train operators before heading out
- Dozens of flights were cancelled from Heathrow after crews and aircraft were left out of position by Sunday's problems. Passengers are advised to check before setting off for the airport
- Travel expert Simon Calder estimated that 50,000 British Airways (BA) passengers were stranded at airports in the UK and around the world on Sunday. The airline said additional staff were rebooking customers on to the next available flights and offering hotel accommodation
- The issues at Heathrow led to dozens of knock-on flight cancellations in Scotland, Cardiff and Belfast
- The Port of Calais reopened after closing for a few hours on Monday afternoon. P&O Ferries is reporting delays of up to two hours on journeys between Dover and Calais. Ferry company DFDS also has delays on its services between England and France
- Eurotunnel said services were now back to normal after some passengers suffered long delays overnight - the firm says conditions remain "very challenging"
- Motoring bodies the AA and RAC are warning drivers to adjust to the conditions "by slowing down and keeping a good distance"
Meanwhile, a trackside fire at London Waterloo added to the delays, causing major disruption to journeys to and from the station.
More than 1,000 homes are still without power after 140,000 were cut off on Sunday.
Western Power Distribution said 900 homes were still cut off, including more than 700 in the West Midlands.
Scottish and Southern Electricity Networks said 750 remained cut off in Oxfordshire.
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