Monday could be the coldest November night in almost 25 years as temperatures plummet towards –8C.
In rural areas, temperatures will drop below –6C (21.2F), while towns and cities — including London — may see the mercury dip to –3C, with the south bearing the brunt of it.
The last time it reached –8C in autumn was on November 22 1993.
Sophie Yeomans, from the Met Office, said: “It’s going to be fairly cold for the next few days … It will be colder down south than up in Scotland on Monday and Tuesday due to the clear skies.”
She added: “While there will be fog patches in some areas such as the north of England, the good news is that there is high pressure which should keep things fairly dry, although there might be the odd spot of rain perhaps on Tuesday and into Wednesday when it gets cloudier.”
The cold snap has also seen bookmakers slash the odds of a white Christmas, particularly in Scotland.
Ladbrokes is offering odds of 2/1 for snow in Aberdeen, Edinburgh and Glasgow; in England, Wales and Northern Ireland, it is offering odds of 3/1 for snow in Newcastle upon Tyne and Belfast.
It is offering odds of 4/1 for London and 5/1 for Liverpool and Manchester.
Jessica Bridge, of Ladbrokes, said: “Winter’s coming, and the odds are falling as quickly as the temperatures are dropping, leaving punters already dreaming of a white Christmas.”
The last official white Christmas was in 2010 when snow was widespread across Northern Ireland, Scotland, parts of Wales, and the Midlands, north-east and far south-west of England.
Winter officially begins on Thursday.