Drivers have been advised to exercise caution on roads in the north and north east of Scotland after heavy snowfalls.
Most roads are open but many are affected by snow and ice to some degree, Northern Constabulary warned.
Police in the Western Isles have asked drivers not travel unless the journey is unavoidable.
About 500 schools have been closed. Aberdeen and Inverness airports suspended flights and Aberdeen to Inverness trains were disrupted.
The Met Office is predicting that heavy snow showers will continue on Friday night in the Northern Isles and Aberdeenshire, while temperatures in the west Highlands could dip to -18C.
BBC Scotland senior forecaster Gail McGrane said the cold weather was likely to continue through the weekend and into next week.
She said: "As we go into the weekend it will be eastern areas which are most at risk of further snow showers with some pushing through the central belt, although much of western Scotland will be dry and sunny but still bitterly cold."
Northern Constabulary said driving conditions were atrocious overnight in Caithness, Sutherland and Easter Ross.
Police and coastguard teams patrolled roads on Friday morning to check no-one had been stranded.
Northern Constabulary said they had to rescue several people near Halkirk in Caithness.
The A9 and the A99 in Caithness, which were closed for several hours, are now passable.
On Skye, the B885 Portree to Struan Road, known locally as Struan Hill Road, and the C1225 Staffin to Uig road, known locally as the Quiraing, are closed.
A police spokesman said: "All remaining roads are open, however most are affected by snow and ice to some degree, in particular in the Western Isles where police are advising drivers not travel unless unavoidable.
"Elsewhere across the force, drivers should continue to exercise extra caution and determine whether their journey could be postponed until weather conditions improve."
In the north east of Scotland, Grampian Police said most major roads were passable with care although many high level minor routes were blocked by snow.
About 500 schools were closed or partially closed in the north, north east, Western Isles and Northern Isles.
The closures included all 23 schools in the Orkney Islands plus Orkney college and all 34 schools in the Shetland Islands.
Only one school in Aberdeenshire was fully open, leaving more than 170 schools closed or partially closed.
More than 60 schools were closed or partially closed in Aberdeen, along with 36 in the Comhairle nan Eilean Siar (Western Isles) area and 130 in the Highlands.
About 35 schools were closed in Moray and four were closed in Argyll and Bute.
The snow also caused disruption at Aberdeen Airport on Thursday where the runway was shut between 1500 GMT and 2000 GMT, leading to cancellations.
It suspended flights again on Friday morning to clear snow and ice.
A spokesman for airport operator BAA advised passengers to check with their airline before travelling to the airport.
The SPL matches between Aberdeen and Motherwell at Pittodrie and between St Johnstone and Dundee United on Saturday have also been called off.
The Scottish government has secured further relaxations of the enforcement of EU drivers' hours rules to help ensure deliveries get to stores, supermarkets and petrol stations across Scotland.
Transport minister Keith Brown visited gritting crews at the BEAR Scotland/Aberdeen City Council shared depot on the West Tullos industrial estate to see first hand the multi-agency response to keep the north-east and Highlands and Islands moving in the face of severe winter weather.
He said: "Everything that can be done is being done and we are working around the clock to deal with the challenges presented by the extreme weather currently being experienced in the north east and north of Scotland.
"A quarter of all Scotland's trunk road vehicles have been deployed in the north-east over the last 24 hours. This includes bringing in additional equipment from Perth and Dundee to help the most affected areas."
He said that an extra 1,000 tonnes of salt were being released from the strategic salt stock immediately for Aberdeenshire Council, and a further 1,000 tonnes would be made available over the Christmas holiday period as required.
Mr Brown added: "While all public agencies are working round the clock and we recognise the high level of collaboration involved, the fact is the conditions we face are atrocious and present real challenges for motorists. It is vital that people across the north of Scotland and the islands pay heed to police advice - travel only as advised."