Snow has been causing disruption across northern Scotland as bitter Arctic weather returns to the UK.
Police in the Highlands are advising against all travel and conditions in the Grampian area are also poor.
BBC weather forecaster Dan Corbett said ice would be a problem for the morning and temperatures would struggle to get above freezing through Friday.
There are heavy snow warnings for northern Scotland, Northern Ireland, Wales, and East and South West England.
High winds and heavy snow showers have combined to produce blizzards across large parts of northern Scotland. On the roads, drifting snow has been the main hazard.
There was a battle to keep major routes open with lorries causing problems south of Inverness on the A82 and the A9. Further north the A9 was closed by snow between Thurso and Brora.
Heavy snow showers have also affected the north-east of Scotland. Traffic in Aberdeen was at a standstill for much of the evening while the runway at the city's airport was closed in the afternoon and early evening.
Several flights were cancelled and an airport spokesman said the disruption would continue to be felt in the morning.
One woman died and three other people were injured in a three-vehicle crash in wintry conditions on the A96 near Huntly, Aberdeenshire, on Thursday morning.
Speaking from a traffic control centre, Scottish Transport Minister Keith Brown insisted he was monitoring the situation and said the authorities were doing all they could to keep trunk roads open.
The BBC has been contacted by people in the Aberdeen area who have reported atrocious road conditions.
Motorist Kirsty McCullough said: "It took me nearly fours hours to do a four-mile round-trip. It's absolutely awful, the roads are sheet ice. They've not been gritted at all."
At Westminster, Energy Minister Charles Hendry has warned that more heavy snow over Christmas could lead to "very serious" shortages of domestic heating oil.
Speaking in the Commons, he said higher demand, coupled with restricted deliveries and soaring oil prices, meant many homes were already having to wait up to four weeks for supplies.
"We are extremely aware that if there is further snow over Christmas, this situation could become very serious indeed," he said.
Jeremy Cole, an oil broker in Cambridgeshire, said domestic oil supplies were already running out and he had been unable to to secure orders for desperate customers before Christmas.
Bad weather has already caused disruption to flights at London Heathrow and Kirkwall airports, and some schools have closed in Shetland, Orkney and Aberdeenshire.
Train services in Scotland were also affected, with cancellations on some ScotRail routes, but Mr Brown has insisted the country is "very well prepared".
His predecessor Stewart Stevenson resigned after his department was criticised for its handling of the problems caused by the previous bout of severe weather.
Motoring organisation the AA said it had extra patrols on standby, while Network Rail also said it had "snow teams in place" and would be "keeping equipment in strategic locations".
A spokesman said: "The main issue we could be facing is ice so we are monitoring temperatures carefully, particularly in the south-east where the third rail is - that's where ice causes most problems because it stops power getting from the third rail to the trains."
Meanwhile, bookmakers have slashed the odds of a white Christmas.
One company, Coral, says the odds have never been shorter - currently 5/4 in London, 4/5 in Aberdeen, 6/5 in Belfast and 11/8 in Cardiff.
But the BBC weather centre said that although forecasters were confident it would stay cold, it was too early to tell where any snow would fall on Christmas Day itself.
Heavy snowfall during the past few weeks has caused huge disruption, especially in Scotland and north-east England.
Airports, roads and schools were closed, and companies are now warning of a backlog of deliveries which may not reach customers before Christmas.
A number of firms, including Tesco, Sainsbury's and Asda, have halted orders or suspended deliveries to Scotland because of the prolonged bad weather.
Royal Mail said it was planning to make 7,000 delivery rounds this Sunday in the worst-hit areas in order to help clear the backlog.