Christmas might not have come early but UK is set to face freezing conditions on the first day of December.
There will be fog patches covering southern Scotland and north-west England in the morning, bring icy weather to -10C in rural areas.
The Environmental Agency has put up 47 flood warnings and alerts across the north-west and south-west.
The rest of the UK remain fine and dry with plenty of sunshine - with temperatures expected not to rise above 6C across the country.
The forecaster said to expect scattered showers likely to happen in the far northern and eastern regions.
Met Office meteorologist Marco Petagna said: "We could see -10C as a cold spell sets in."
The cold air strip continues into Monday, bringing outbreaks of light rain or drizzle in Scotland, while Northern Ireland will be dry, but cloudy at times.
BBC meteorologist Louise Lear said: "In the UK we start Sunday with high-pressure coming in from the West.
"Temperatures are likely to struggle tomorrow, just below where they should be for this time of year.
"The temperatures will be up to 3C at the very best in some areas, with others reaching at most 8C."
5-day weather forecast
Today:
Most places dry and sunny, but feeling cold. Fog patches slow to clear in parts of southern Scotland and north-west England. Scattered showers likely in the far north and east.
Tonight:
Dry and clear for many with widespread frost. Fog patches across some western areas. Showers in the far north of Scotland merging into more persistent rain later.
Monday:
Another dry and sunny day for most, but rather cold. Windy with outbreaks of rain in far north of Scotland.
Outlook for Tuesday to Thursday:
Cold and dry in the south with some sunshine but also frost and freezing fog. Milder in the north, but windy at times with some rain, especially on Thursday.
