The Queensferry Crossing has reopened after being forced to close for four hours following heavy snow.
Hundreds of people reported hearing “extraordinarily loud thundersnow” during the night in Edinburgh, with many reporting the noise to police.
Thundersnow occurs when thunder and lightning combines with a heavy snowstorm.
Roads were closed across Scotland and public transport was affected, while the Met Office issued a yellow ‘be aware’ warning for snow and ice.
Traffic Scotland warned motorists of the Queensferry Crossing closure around 6am, adding that the Forth Road Bridge had also been closed due to planned works and urged drivers to divert via the Kincardine or Clackmannanshire bridges.
But it reopened just after 9am, with roads maintenance firm BEAR Scotland saying falling ice had forced the closure.
Chris Tracey, BEAR Scotland’s South East Unit Bridges manager, said: “The risk of falling ice has now passed and it is safe to reopen the bridge. We apologise for any inconvenience caused to road users by this closure.”
The M74 was also closed until around 10am southbound between junctions 10 and 15, leaving drivers stuck for hours, while gritters were out across most of the country.
ScotRail said that heavy snow was affecting train services across the network, and urged travellers to check their route before setting off.
Meanwhile, some people contacted police to raise concerns after they heard strange noises amid stormy weather.
Police Scotland Control Rooms tweeted at around 5am on Friday: “We have received a number of calls regarding people concerned about explosions heard.
“Please do not be alarmed, we are currently experiencing thunder and lightning.”
STV weather presenter Philip Petrie said: “Many of us woke up to very wintry conditions today.
“Yesterday the worst affected areas were in the west, where overnight sleet and snow showers meant a dusting of snow to start the morning.
“It’s a reversal of fortune today, as the east sees the brunt of persistent rain moving in from the North Sea.
“As that rain hits the cold arctic air that is currently pushing down from the north, it’s turned into sleet and snow – affecting many eastern areas such as Aberdeenshire, the Lothians, Angus, Fife, Perth and Kinross and Dundee.
“Throughout the day the snow will become confined mostly to higher ground, and the yellow snow weather warnings in the east switch to rain weather warnings, as the wet weather continues to feed in from the east through the afternoon.
“We’ll also have very strong, possibly gale force, northerly winds today which, added to the rain, sleet and snow, means it will be feeling a lot chillier than the forecast temperatures.”