Cold winds, frost and even some snow are to hit Britain this week, signalling the end of the October heatwave.
The mercury peaked at an unseasonably high 18.3C in Gravesend, Kent, on Saturday but temperatures are set to drop in the coming days.
Andy Ratcliffe, a forecaster at MeteoGroup, said: "A cold front will start across Scotland and Northern Ireland on Monday, giving some heavy outbursts of rain which will turn to snow over the mountains in Scotland.
"The rain will spread further south into northern England and Wales by the end of the day."
Winds of up to 65mph are expected across north-western England, Scotland and Northern Ireland, and the odd rumble of thunder is possible.
"We will definitely feel a chill in the air," Mr Ratcliffe said. "The winds originate in the Arctic, but they get modified a lot as they arrive here."
Although the south of the country will enjoy highs of up to 17C on Sunday and into Monday, , it will feel much cooler across the UK on Tuesday, with highs of 14C in the south and 10C in Scotland.
On Wednesday night, temperatures will plunge to around 1C and could be as low as -1C in northern parts of the country.
Mr Ratcliffe said: "It's going to be pretty cold everywhere across the UK on Wednesday night, with widespread ground frost expected in the whole of the UK and perhaps air frost in places too."
However, by the end of the week conditions should be milder as a result of weather systems moving in from the Atlantic.