Temperatures in a hamlet in northern Scotland dropped to -18.9C (-2F) in the early hours of Saturday – the UK’s coldest January night in 15 years.
It is the coldest January overnight temperature since 2010, when they dropped below -15C several times at locations across the UK, including -22.3C on 8 January in Altnaharra.
The average low in northern Scotland for this time of year is about 0.3C, while for England, overnight lows are about 1.5C to 1.6C.
Temperatures were widely around -4 to -10C on Saturday morning with some freezing fog in parts of the Midlands and eastern England.
More than 50 schools were closed in the Highlands on Friday, with 13 shut in Aberdeenshire.
Hundreds of other pupils also had another day off due to closures in Moray, Shetland and the Outer Hebrides.
Meanwhile, the UK Health Security Agency (UKHSA) has extended its cold weather health alert for all of England until Tuesday.
Amber alerts have been extended and will now run until 14 January, meaning a rise in deaths, particularly among those aged 65 and over or with health conditions, is likely, the agency said.
Meanwhile, with some milder air spreading into Northern Ireland, west Wales and south-west England, temperatures stayed above freezing at 5 to 10 C.
While the less cold air in the west will bring some cloud and some light rain at times, for most of the UK, Saturday will be another cold day with temperatures not much above freezing.
Temperatures will drop quickly on Saturday night again across eastern areas, especially in north-east Scotland where it could be as low as -15C.
But overall, Sunday morning will not be as cold as previous mornings.
The day will be mostly dry with wintry sunshine and with milder air moving a little further north and east, temperatures will not be as cold again.
Very gradually, higher than average temperatures will spread across many parts of the UK through the coming week, with maximum temperatures of 10-14C from Tuesday and Wednesday onwards.
This could lead to a significant thaw of all the snow and ice that may lead to higher river levels and a risk of flooding in places.