The northern peaks will be battered by strong winds which could whip falling snow into a blizzard.
As the band of rain currently soaking the south east of England moves to the east this evening, a cold front will course in behind it.
With it comes freezing temperatures which will see rain, sleet and snow fall on the UK's mountains.
The conditions up high will be made more intolerable by furious winds blowing in from the west.
Peaks in Snowdonia, the norther Pennines and the Highlands will hit by snow over the coming weekend.
The wintery conditions will be the most intense on Saturday, when snow could settle on hills as low as 200m in Scotland and northern England.
Matthew Box, forecaster at the Met Office, said: "We have strong wind warnings out for Friday in south east Scotland and north east England. They could hit 55mph to 65mph.
"There will also be widespread coastal gales across the north of Scotland and Northern Ireland.
"We could have blizzard conditions at a time if you're stuck on the top of a mountain."
The meteorologist predicted there could be 20cm of snowfall on the mountains of Scotland, although patchy rain made it difficult to forecast.
Snow is already falling across parts of Snowdonia National Park and the hills in north and central Wales, according to radar images.
A yellow weather warning for rain remains in place for two areas of Wales - one in the north west from Colwyn Bay to near Aberystwyth and one in South Wales, including Cardiff and Swansea - until 2pm.
There is also a warning in northern England, Northern Ireland and parts of Scotland.
Residents in those areas may experience rainfall of 70-100mm by the time showers come to an end.
While cold air will grip the country, plummeting temperatures into the low single digits on Thursday night.
BBC senior forecaster Derek Brockway tweeted: "Sharp cold front and rain moving across the #UK this morning.
"Snow falling on the hills and mountains in #Wales. Drier, clearer weather over #Ireland with broken cloud, sunshine and scattered showers. Turning noticeably colder with a drop temperature and change in wind direction."
According to the Met Office, parts of South Wales, including Cardiff, Newport and Swansea will feel like 1C.
Areas along the coast may feel even colder, with some places expected to feel like -1C.
But temperatures are expected to climb to around 7C around the coasts and as high as 10C for inland areas over the weekend.
Saturday and Sunday will feature similar temperatures, though rain and strong winds are expected to return.
