Temperatures in a hamlet in northern Scotland fell to -18.7C (-1.66F) overnight - the UK's coldest January night in 15 years, the Met Office has said.
Altnaharra, in the northern region of the Highlands, reached the lowest temperature while nearby Kinbrace reached -17.9C (-0.22F).
It is the coldest January overnight temperature since 2010, when temperatures dropped below -15C several times at locations across the UK, including -22.3C (-8.14F) on 8 January in Altnaharra.
Forecasters had previously said there was a very small probability it could reach -19C.
Met Office meteorologist Alex Deakin said: "Friday night into Saturday morning may well be the nadir of this current cold spell."
Temperatures for large parts of the UK are set to fall again as the cold weather continues.
Met Office meteorologist Zoe Hutin said: "We've still got tonight to come, and tomorrow (Saturday) night could also be chilly as well.
"Temperatures for tomorrow night, it will be mainly eastern parts that see temperatures dropping widely below freezing, so East Anglia, the northeast of England, northern and eastern Scotland as well.
"So another chilly night to come on Saturday, but then as we go into Sunday and into Monday, then we can start to expect temperatures to recover somewhat.
"I won't rule out the risk of seeing something around or just below freezing again on Sunday night into Monday, but it won't be quite so dramatic as the temperatures that we're going to experience as we go overnight tonight."
On Monday, temperatures are expected to be more in line with the seasonal norm, at about 7C to 8C.
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The freezing conditions have led to travel disruption, with Manchester Airport closing both its runways on Thursday morning because of "significant levels of snow". They were later reopened.
Transport for Wales closed some railway lines because of damage to tracks.
Hundreds of schools in Scotland and about 90 in Wales were shut on Thursday.
Meanwhile, staff and customers at a pub thought to be Britain's highest were finally able to leave on Thursday after being snowed in.
The Tan Hill Inn in Richmond, North Yorkshire, is 1,732 feet (528m) above sea level.
Six staff and 23 visitors were stuck, the pub said on Facebook.
(c) Sky News 2025: UK weather: Scottish hamlet reaches -18C in coldest January night in 15 years
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