Britain's early summer was brought to an abrupt halt as snow blanketed parts of the country on Tuesday.
Scotland was the worst affected, with snow falling in the Highlands, and dusting central parts of the country.
As an Arctic weather front bore down on the UK, the Met Office issued severe weather warnings for all of Scotland, as well as parts of northern England, Yorkshire and Humber, and the East Midlands.
A major rescue operation was launched in the morning after a group of hillwalkers became stuck in the Cairngorms.
The three adults and six teenagers were stranded following the overnight snowfall.
Grampian Police, a Royal Navy helicopter and a mountain rescue team based at Braemar, Aberdeenshire, were all involved in the operation to rescue them from the hillside.
Around four hours after they were alerted, police confirmed that all nine hillwalkers had been rescued successfully. They were found at Derry Cairngorm, a mountain in the Cairngorms range.
The walkers were airlifted off the hillside and taken to the Braemar area by the Navy helicopter.
There were a number of minor collisions and reports of cars sliding off the road in Tayside and Fife where some vehicles also became stuck in the snow in the Largoward and St Monans area.
The wintry blast comes just a week after record-breaking warm temperatures in north-eastern Scotland.
Last Tuesday temperatures rose to 23.6C in Aboyne, Aberdeenshire, marking a new high in Scotland for the month.
Today the mercury dropped to minus 0.5C overnight and was at 0C at 6am.
Around four inches (10cm) of snow has carpeted most parts of northern Scotland overnight, with accumulations of 7.5 inches (17cm) recorded in Aviemore in the Highlands and temperatures of minus 2.7C in Glen Ogle.
Scotland's central belt was also hit by the wintry weather, which will gradually creep into northern England, parts of Wales and the Midlands in the coming 24 hours.
Scottish Transport Minister Keith Brown told BBC Radio Scotland: "This kind of weather is much more normal for Scotland than the superb weather we have had over the previous days. So we have had, for example, 124 gritters out overnight."
Motorists in affected areas were told to drive with the "utmost care".
Police dealt with a number of incidents, including a three-vehicle collision in "whiteout conditions" near to Tullybaccart Farm in Blairgowrie, Perthshire.
Four people were taken to hospital after a car left the A90 at the St Ann's to Keithock junction in Brechin and came to rest in a ditch.
Meanwhile, five people, including two young children, were taken to hospital after being involved in a two-car collision on the A9 at Skiach, Evanton in the Highlands.
A woman, who was a passenger in one of the vehicles, had to be airlifted to hospital with serious injuries.
The woman driver and two children from that car and the woman driver from the other vehicle were all treated at the scene and then transferred to hospital by ambulance.
Northern Constabulary said they do not know if the crash was caused by the bad weather.
Meanwhile, engineers are working to restore power to parts of the country cut off by the snowfall.
This morning 11,000 Scottish Hydro customers were left without power. Tayside was the worst hit, with 6,000 customers cut off, while 3,000 were without power in the North East and 3,000 in the Highlands.
Scottish Hydro said engineers are working to fix the power cuts but by 1.15pm more than 6,000 people were still without a supply.
The company said it hopes to have its customers reconnected by early evening.
Forecasters predict that the snow will continue to move south, passing over the north of England and moving into the Midlands by tomorrow morning.
Aisling Creevy, a forecaster with MeteoGroup, the weather division of the Press Association, said: "Tomorrow the UK will be noticeably colder and feeling quite raw and we could get widespread lows of around minus 5C in Scotland overnight."
The weather is in stark contrast to March's hot weather: the only years to have had a warmer month in the past 100 years are 1938, 1948, 1957, 1990 and 1997.