The coldest night of winter so far could be approaching, with some areas forecast to hit temperatures as low as -10C.
Scotland and northern areas of England and Ireland will see what could be the lowest temperatures of the season on Monday night, according to the Met Office.
Snow is forecast for the highlands and high-level areas of northern England, where yellow weather warnings for ice are in place.
Ice is also expected to sweep the rest of the country throughout the day, even reaching the south coast.
Overnight temperatures will range from -10C in sheltered areas of Scotland, to between -1C and -2C in Cornwall and Dorset.
Four weather warnings have been put in place by the Met Office for snow and ice in the north, with roads and railways set to be ground to a halt in places.
While 33 flood alerts has also been issued, largely across south west and up to the Midlands, by the Environment Agency.
Met Office Meteorologist Simon Partridge said: "There's potential that we could see the coldest night of winter so far on Monday night going into Tuesday morning.
"It depends if we have clear skies over snow for long enough.
"This leads to cold temperatures, and we'll certainly have two cold days.
"Sleet and snow showers are forecast for Monday, which will bring icy patches to low ground and snow to higher ground."
He added a chilly breeze will also add to the wintry climes on Monday and Tuesday, although daytime temperatures will be near the average of around 2C for this time of year.
The sudden plummeting temperatures are thanks to an "ice blast" from Greenland.
Experts say a change in wind direction is to blame for the chill as the bitter Arctic air sends thermometers plunging.
Rain showers will turn increasingly wintry through Monday, with around 2-3cm of snow is expected in the Pennines and in Scotland.
Helen Roberts from Met Office said: "It's going to be a shock to the system for many due to recent warmer temperatures."
Luckily, the wintry weather is set to be a "short sharp cold spell" over two days before milder weather moves in on Wednesday.
UK 5 day weather forecast
Today:
Frequent and often heavy wintry showers in north-west Scotland continuing throughout the day. Elsewhere showers mainly around western and southern coasts moving further inland, becoming more persistent later. Best of drier and sunnier spells in north-east England. Windy.
Tonight:
Area of rain and sleet moving across parts of Northern Ireland, southern Scotland and northern England, with snow, chiefly over hills. Clear intervals and showers elsewhere, turning wintry. Icy patches.
Tuesday:
Sleet and snow over southern Scotland soon clearing, else cold and breezy with sunny spells and showers, these wintry at times. Showers heaviest in the north and west.
Outlook for Wednesday to Friday:
Continuing unsettled with showers or longer spells of rain, heaviest across western Scotland. Best of the drier weather in southeast England. Milder than of late, but with strong winds.
