Weather warnings for snow and ice have been issued for parts of the UK, with 10cm of snow forecast in some areas.
Parts of the western Highlands have already seen flurries.
The warning came into effect at 2pm on Monday and will last until midnight, although there will be a risk of ice across most of the UK from around 9pm until early on Tuesday.
While the snow is more likely to be seen on higher ground, forecasters say there is a chance of it reaching lower levels along with sleet.
Simon Partridge, of the Met Office, said: “It’s already picking up over the western Highlands and is most likely over the high grounds with guaranteed snow at 200-300 metres.
“For now, after the main band is cleared up by about 9/10pm, showers will follow, meaning sleet and snow will lap up on any snow already there.
“You’re looking a potential case of nearly 10cm of snow in areas above 500m.
“Some snow could be seen on the lower levels, so it’s not exclusively left to the high ground – but it could end up being rain, snow, rain.
“So, on and off there could be snow from now until the early hours of Wednesday for the west of Scotland, and the best part of 24 hours.”
Temperatures in the early hours could drop to as low as minus 2C (28.4F) in Pitlochry while Southampton may see highs of 7C (44.6F).
He added: “The main problem is that skies become clear so there’s an ice risk after midnight which could cause some big issues during the overnight period.
“There’ll be further showers tomorrow with some hail and sleet along the coasts, on the hills and mountains you can see it turning into snow.”