The Met Office says an overnight temperature of -22.9C recorded in Scotland is believed to be the lowest in more than 25 years.
BBC weather presenter Simon King described the temperatures in Braemar, Aberdeenshire, as “incredible”.
The Met Office said it was provisionally the coldest night since 1995.
ScotRail said the winter weather was causing major problems for its services on Thursday morning.
A Met Office yellow snow and ice warning is in place for large parts of the country until 12:00 on Friday.
Malcolm MacIntyre, of the Braemar Mountain Rescue Team, told BBC Radio’s Good Morning Scotland: “It is a beautiful morning actually and it is really cold.
“The snow is squeaky, which always signifies that it is really cold.
“But in some ways once it gets below about minus 10/12, as long as it is not windy, it just feels really crisp and clear.”
Traffic Scotland urged drivers not to leave home unless it is essential and ScotRail is encouraging people to check their journey before leaving the house.
The operator tweeted: “We’re currently seeing severe disruption across the network, particularly in the Central Belt with disruption affecting services to/from Glasgow Queen Street High Level and Edinburgh Waverley.”
On Tuesday heavy snowfall caused widespread disruption across Scotland.