Temperatures plunged to -16C (3.2F) overnight making it the coldest night of the winter so far.
The figure was recorded at Holbeach, Lincolnshire, and temperatures were down to -10 to -15 across some other parts of England and Wales.
However, Scotland and Northern Ireland were largely frost free overnight.
BBC weather forecaster Laura Tobin said it would stay very cold, with freezing fog affecting parts of the east Midlands and Lincolnshire.
On Friday dozens of schools in England closed, including 30 in Staffordshire and Cheshire, one in Wiltshire, four in Lincolnshire and two in Cambridgeshire, after snow had fallen overnight.
The Met Office also issued "yellow" warnings, telling people to "be aware" of ice up to midday on Saturday across England and Wales.
http://www.bbc.co.uk/news/uk-16959950