Temperatures will dip below zero as the record-breaking mild New Year conditions are replaced by a more unsettled weather picture, forecasters said.
Snow fell in Scotland and parts of northern England on Tuesday, and overnight temperatures from Wednesday into Thursday are expected to dip below freezing during a cold snap.
Strong winds, coupled with the snow, have led to treacherous travelling conditions in northern Scotland.
The Met Office warned of 60mph-70mph gusts, possibly stronger for a time, for Orkney and Caithness.
Strong winds on Tuesday also affected a number of ferry services operating in Scotland.
Met Office spokesman Richard Miles said: “It’s going to be colder than we have been used to over the last couple of days and Christmas.
“We are going into a period when temperatures will be dropping quite a bit.”
⌚️09:41— Traffic Scotland (@trafficscotland) January 4, 2022
Heavy snowfall affecting many routes including the #A87 #A82 #A95 #A9 and #A90
A @metoffice YELLOW weather warning remains in place today for SNOW and ICE❄️@PoliceScotland have also issued travel with caution warnings@NWTrunkRoads @NETrunkRoads @HighlandCouncil pic.twitter.com/heWOGwn0qE
A band of rain is moving from south-west England, south-east Wales and across to the Wash, gradually moving east, with wintry conditions on higher ground.
Snow warnings have been issued for the Highlands of Scotland, with snow also having fallen on the Pennines in northern England.
Blustery, wintry showers are expected to continue, with more snow expected on higher ground in England and Wales.
On Wednesday a ridge of high pressure will bring dry conditions for most of the UK, along with showers on the North Sea coast from time to time.
Temperatures will fall to below freezing overnight into Thursday, giving the UK the first widespread frost of the winter, Mr Miles said.
Looking towards the weekend, temperatures are expected to rise slightly, but the picture remains unsettled with wintry showers expected for some.
A weather warning for snow in built-up areas of Scotland remains in place for Friday.