Temperatures plunged to below minus 22C overnight, the lowest in the UK in more than two decades, following an “extreme freeze”.
The mercury dropped to minus 22.9C (minus 9.2F) in Braemar, Aberdeenshire, the coldest temperature recorded in the UK since 1995, the Met Office said.
Forecasters said the last time a temperature below minus 20C was recorded in the UK was December 23 2010.
Scattered snow showers and some sunshine is forecast for large swathes of the UK over the rest of the day on Thursday.
Yellow weather warnings for areas where wintry weather could cause travel disruption have been issued for the morning, covering the eastern half of Scotland and England, Devon, and south-west Wales.
As the snow clears towards the east through the morning, it could become “quite pleasant outside with the sunshine, although still bitterly cold” in western areas, according to Met Office meteorologist Clare Nasir.
The latest plunge in temperatures comes after Tuesday night, when minus 17.1C (1.2F) was recorded in the Scottish Highlands.
That marked the coldest temperature recorded in the UK since January 2010, when the mercury dropped to minus 22.3C (minus 8.1F) at Altnaharra in the Highlands.