Police have urged people to consider delaying any essential journeys after the Met Office issued an amber warning of heavy snow across parts of Scotland.
The warning means there is a potential risk to life and an increased chance of travel disruption and power cuts.
It covers the Highlands, Grampian, Tayside, Central, Fife, the Lothians, Strathclyde, Dumfries and Galloway and the Scottish Borders.
Transport Scotland has warned of potential travel disruption.
People should only be leaving home to make essential journeys in parts of Scotland under level four Covid measures, under current Scottish government lockdown regulations.
The amber warning for up to 20cm (8in) of snow on higher ground takes effect from 15:00 on Wednesday.
The Met Office said up to 10cm (4in) was likely at lower levels by Thursday morning.
The alert, which also extends to parts of north east England – including Durham and Newcastle – is in place until 10:00 on Thursday.
A yellow warning of snow and ice for much of the rest of the country remains in place until 21:00 on Thursday.
Ch Supt Louise Blakelock, of Police Scotland, said: “Government guidance on only travelling if your journey is essential remains in place and so with an amber warning for snow, please consider if your journey really is essential and whether you can delay it until the weather improves.
“If your journey really is essential, plan ahead and make sure you and your vehicle are suitably prepared by having sufficient fuel and supplies such as warm clothing, food, water and charge in your mobile phone in the event you require assistance.”
Transport Secretary Michael Matheson has asked people to heed the warning and to follow advice from police and Traffic Scotland.
He said: “The conditions will likely cause difficult driving conditions and disruption to the wider transport network, so it’s important that anyone that has to make an essential journey during the warning period plans their journey.
“The current Covid restrictions mean you should only be leaving your home for an essential purpose, so please consider if your journey is absolutely necessary before setting off.”
Police in Shetland have also warned of ice badly affecting roads on the islands.
Scottish Borders Council said the effects of the adverse weather could cause disruption into Friday morning.
Emergency planning officer Jim Fraser said: “With widespread snow and some freezing rain possible over the course of Wednesday and Thursday, there is the strong potential for disruption across our road network and communities.”
Parts of Scotland have experienced wintry conditions since the end of last month. Parts of the Highlands, including Inverness, had heavy snow showers on Monday.
Some of the deepest snowfalls in recent weeks have been in the Highlands, including the Cairngorms.
Earlier this month, the UK had its coldest night of the winter so far after a temperature of -12.3C was recorded in the north west Highlands.
The temperature was recorded at Loch Glascarnoch, near Garve, south of Ullapool in Wester Ross.
The record lowest temperature in the UK is -27.2C, which was recorded in Braemar, Aberdeenshire, in 1895 and 1982 and at Altnaharra in the Highlands in 1995.