Parts of the UK will be up to 19C (66F) warmer tonight compared to last night as the cold snap begins to ease.
The village of Kinbrace in the Scottish Highlands fell to -13.9C (7F) on Saturday night – but is expected to be well above freezing in the small hours on Monday, at about 5C (41F).
At this time of year, the average low in northern Scotland is around 0.3C.
Also on Saturday, Cavendish in Suffolk hit -7.8C (18F) and Hawarden Airport in Wales dropped to -2.2C (28F), the Met Office said.
Fog accompanied the freezing conditions on Sunday morning – and was expected to take time to clear.
While the UK Health Security Agency has extended its cold weather health alert for all of England until Tuesday, temperatures are forecast to rise.
Milder air will arrive on Sunday night, and once the small hours have passed, temperatures in Northern Ireland and western Scotland could be as high as 9 or 10C on Monday morning.
Most other places are forecast to be between -1C and -3C – still chilly, but warmer than recent nights.
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On Tuesday, temperatures are expected to be between 11-12C in the north and 8-9C in the south.
“[It will be] back to average temperatures generally for the time of year,” said Met Office meteorologist Greg Dewhurst.
