Met Office amber weather warnings are in place for snow across Shetland, Orkney and parts of northern mainland Scotland from 18:00 GMT on Sunday until 10:00 on Monday.
Heavy snowfall over recent days has resulted in more than 40cm reported in parts of Moray already.
Strong winds have been causing drifting, with Network Rail Scotland reporting snow drifts up to 1.2m (4ft) on the line between Aberdeen and Dundee.
Scottish regional airline Loganair has cancelled flights from Aberdeen and Inverness airports on Sunday and Monday following heavy snowfall.
As the snow showers become heavier and more frequent during Sunday night, the Met Office is warning for the potential of another 20 to 30cm of snow.
Further road and rail closures are possible and disruption to power is likely in some areas too.
The Met Office also warned that mobile phone coverage could be affected.
Hundreds of schools in northern Scotland will stay shut after the Christmas holidays on Monday.
The return of pupils has been delayed in Aberdeenshire, Shetland and Orkney, while schools in Aberdeen will have a later start.
A number of schools in Northern Ireland will also be closed on Monday. A full list is available here.
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