Icy conditions, snow and freezing rain have been reported in Scotland and northern England as Storm Deirdre arrives.
The Met Office has issued weather warnings for snow, ice and freezing rain, saying that a "rapid development of widespread ice" in central England will make dangerous travelling conditions likely.
A number of roads in northern England and Scotland have been closed and vehicle collisions have been reported in various parts of the UK.
One of the roads worst affected was the M74 in Scotland between Junction 15 (Moffat) and 17 (Lockerbie), where police blamed icy conditions for a number of accidents. There was also heavy snow and treacherous conditions reported on the A9 between Perth and Aviemore in Scotland.
The Met Office also said that a gust of 71mph was recorded in Pembrey Sands, Wales, on Saturday evening.
Ireland's meteorological service, Met Eireann, issued an orange warning – similar to the Met Office's amber warning – for wet conditions and gusts of up to 80mph (130kmh).
As of 9pm Saturday, the Met Office had one amber warning in place for heavy snow and blizzards in central Scotland.
There were also three yellow warnings: one for snow and ice in most of Scotland and northern England, and two for wind – severe gales over the Northern Isles of Scotland and parts of Caithness and strong winds around coastal Wales and northwest England.
On higher ground there could be between 10cm and 20cm of snow, with 40cm falling on the highest peaks in Scotland.
At lower levels there will be up to 5cm of snow in parts of Scotland and northern England.
The warnings last until 6am on Sunday.
Only London and the South East have escaped the warnings but those areas could still see some heavy rain.
There is a chance of injuries from slips and falls on icy surfaces, the Met Office said, and bus and train services may be delayed or cancelled, with some road closures and longer journey times possible.
The Met Office's chief meteorologist, Steve Willington, said: "At the moment, the heaviest snow is expected over higher ground in Scotland with the chance of drifting snow due to strong winds.
"Snow is also expected to settle at lower levels in Scotland and parts of northern England, with the risk of freezing rain and ice on Saturday night."
Superintendent Louise Blakelock, deputy head of road policing for Police Scotland, said: "Freezing rain is highly unusual and is expected to result in the rapid development of widespread ice, which will lead to dangerous travelling conditions," she said.
"I appreciate that many people will be planning Christmas shopping trips this weekend and have festive social events planned with family and friends; however, if you do travel, you are likely to experience significant delays.
"Congestion caused by all vehicles may restrict the emergency services, recovery vehicles, gritters and snowploughs from providing essential assistance or from clearing roads."
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The cold weather is being triggered by an active low-pressure system moving in from the Atlantic.
The good news is the cold weather is not expected to last long, with temperatures expected to creep back up to 8C or 9C at the start of next week.