Fresh amber "be prepared" warnings of snow and ice have been issued for parts of Scotland.
Forecasters warn that delays on the roads and public transport cancellations are likely, while vehicles may become stranded in some places.
The Met Office warning, which covers Tayside, Fife, central and southern Scotland and Strathclyde, is valid until 10pm on Friday.
It warns of heavy snow showers with up to 12in (30cm) possible over the highest routes, and up to 4in (10cm) at lower levels.
Forecasters said there is a chance of power cuts, while some rural communities may be cut off.
Police Scotland warned there is a "high risk" of disruption and urged people to drive to the conditions.
Superintendent Louise Blakelock, of Police Scotland's Road Policing department, said: "We've been working closely with our colleagues at Transport Scotland, the Met Office and local councils to assess the conditions.
"Therefore, for the duration of this updated warning, there is a high risk of disruption for road journeys and there is a high likelihood of the conditions for travel being very poor.
"Those heading out on the roads should be aware of these risks - ensure you have a fully charged phone, warm clothing, and leave extra time for your journey.
"Drive to the road conditions and make sure you check the most up-to-date information from Traffic Scotland and the Met Office before heading out. Our priority is to ensure the public are safe."
First Minister Nicola Sturgeon urged people to be careful, tweeting: "Travel conditions likely to be difficult so please take care, follow advice @trafficscotland - and only travel if you have to."
Some schools in the Borders, South Lanarkshire and the Highlands are closed due to the weather.
A yellow "be aware" warning of snow and ice for most of Scotland, Northern Ireland and North West England is in force until 11.55pm on Friday.
It warns of frequent snow showers which will be accompanied by hail and lightning at times, particularly across western Scotland.
There are warnings of ice in north-east England, Wales, south-west England, the West Midlands, and Yorkshire and Humber on Friday morning.