Heavy snow affected routes across the country, including the main motorways, after the Met Office issued an amber "be prepared" warning for much of Scotland, Northern Ireland and northern England.
Tulloch Bridge in Inverness-shire saw the deepest snow in Scotland with 23cm (9ins) while there was 9cm (3ins) in Aviemore.
Further snow is now expected.
A missing woman was airlifted to hospital after she was found unconscious in blizzard conditions in the Scottish Borders, while a car skidded on ice and fell off the road into the basement area of a building in Edinburgh.
A Royal Navy Search and Rescue helicopter was used to help a sick one-year-old who had become stranded in a house near Langholm because of the snow.
The youth was airlifted to hospital in Carlisle by a sea king helicopter after an ambulance became stuck in the snow and an air ambulance from Glasgow was not cleared to fly, reported the Royal Navy.
Out of the 122 schools in Dumfries and Galloway, 80 have been closed because of the weather.
BBC Scotland's Willie Johnston has reported "dreadful conditions" on the A75 near Carrutherstown.
Meanwhile, Highland Council said 18 schools and nurseries in its area are closed because of the weather.
About 10 others have been closed to pupils who have to travel by bus, or were opened later.
Scottish Borders Council said three of its schools were closed, while eight schools were shut in South Lanarkshire, along with two in South Ayrshire.
Flights at Inverness Airport and Kirkwall Airport were disrupted on Thursday morning while the M9 was closed for an hour between junction 5 (Bo'ness) and junction 6 (Falkirk) after a cattle lorry overturned.
The Met Office has issued yellow "be aware" warnings for all of Scotland for the remainder of Thursday and Friday.
The warnings will remain in place for northern and western regions of the country for Saturday, Sunday and Monday.
Showers of sleet, snow and hail are expected to continue through Thursday and Friday morning.
Between 1-3cm of further snow could fall on lower levels.
More snow and strong winds are forecast for the north and west of Scotland on Saturday and Sunday.
BBC weather forecaster Darren Bett said icy conditions were expected to follow the snow on Thursday.
He said: "Tonight ice is going to be more of a concern.
"We have a band of wetter weather moving down from the north later in the evening. Overnight most of it will fall as rain, but there will be snow on the highest ground.
"But there will be breaks in the cloud and skies will clear again, so tricky for the gritters tonight and tricky for anyone on the roads."
Ch Supt Iain Murray, from Police Scotland, urged motorists to carefully plan their journeys and said localised conditions could make driving difficult.
"If you do decide to travel, ensure your vehicle is well prepared before setting off; make sure your windscreens are completely free of snow and ice, and your lights are working and clean," he said.
Check out the latest travel news for Scotland
For the latest on the roads visit the BBC's travel news page and keep up to date with incidents and roadworks on the motorways here.
Around the country you can check for updates from:
Alternatively, for regular travel bulletins listen live to BBC Radio Scotland and follow @BBCTravelScot.
In times of severe disruption you can also follow the BBC Scotland severe weather Twitter list of key sources.
Below are a number of other traffic information sources.
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Wintry weather has caused hazardous driving conditions across parts of Scotland and has led to more than 100 school closures.
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