The Met Office has issued an amber warning for heavy snow overnight across parts of Wales.
It comes after motorists faced disruption and hazardous road conditions on Saturday following a second day of snow and icy weather.
The main A55 dual carriageway from Denbighshire to Flintshire remains "treacherous" after snowfalls during the day.
Public transport across the south Wales valleys was also affected.
On Sunday, an amber warning for snow is in place for large parts of north and mid Wales from 04:00 GMT to 18:00.
A yellow warning for wind is also in place for south Wales.
There have been several road closures in the last 24 hours due to snow and icy conditions, and nearly 200 schools shut on Friday.
In Rhondda Cynon Taff, the A4233 Maerdy mountain road was shut overnight in both directions between Maerdy and Aberdare, while bus operators Stagecoach Wales warned many passengers that it would only be operating on main road stops in some areas.
The weather led to Red Cross' emergency response volunteers being called in to help Betsi Cadwaladr University Health Board transport staff, equipment and blood supplies to hospitals in north Wales.
Conwy and Gwynedd councils said they remained prepared for the wintry weather, with well stocked salt reserves and gritting vehicles working to keep priority routes clear.
Denbighshire council said its gritting teams have been out all night, helped by agricultural contractors. However, the A542 Horseshoe Pass remains closed near Llangollen.
Officials in the county said they were preparing for more snow on Sunday, following the Met Office's amber alert.
In Powys, the county's head of highways said they were expecting the "most significant winter weather event for a number of years".
"Our Powys specific forecast indicates extended periods of sub zero temperatures and significant snowfall," said Nigel Binn.
Taking his message to social media, he added: "Road conditions will be particularly challenging across the county over the next 24 hours. Please only travel if it's necessary and if you have to, please take extra care."