Snow, hail and thunder could hit Britain in the next couple of days before a temperatures are sent plummeting again at the weekend.
The Met Office is expecting a chilly day today for northern England, with heavy rain in Scotland and Northern Ireland.
Further south it will be milder and mostly dry, but patchy dry and drizzle further north.
Tomorrow, the south-east will be bright and mild, but wintry showers are expected further north and in Scotland and Northern Ireland, with heavy rain, snow, hail and thunder possible.
In a topsy-turvy outlook for the country, mild weather further south could simultaneously bring the warmest day of the year.
The Weather Outlook forecaster Brian Gaze said: “The 18C warmest days of the year are possible before the chill, as floods finally ease.”
The weekend is expected to be much colder, with fine and bright weather, but chilly nights bringing widespread frost.
Met Office forecaster John Griffiths said: “Temperatures will be the mildest this year, with a chance of 17C on Tuesday or Wednesday in the South.
“But colder air from near Norway and then from the Baltic Sea spills across the whole country by Friday, until Sunday.
“-3C could be seen in the South and North, with widespread frost and some wintry showers over the North and East.
“But there will be plenty of dry spells this week with much lighter rain than previous weeks. And ahead looks to remain drier, with plenty of sunshine for most.”
Today:
The far north chilly, bright but showery, while heavier rain returns to much of Scotland and Northern Ireland. Further south, mostly dry, mild, windy with occasional brightness, but patchy rain and drizzle affects western hills and far north of England.
Tonight:
Rain sinking southwards, allowing colder, showery weather across the north: some heavy showers, wintry on hills. The south and east of England staying mainly dry and mild.
Wednesday:
Showery across Scotland and Northern Ireland, with some heavy showers, hill snow and possible hail and thunder. Rain and drizzle slowly edging southwards but the far southeast bright and mild.
Outlook for Thursday to Saturday:
Sunny spells and wintry showers in the north Thursday; cloudy in the far south. Fine and dry elsewhere, these conditions spreading to most areas by Saturday. Cold with night frost.
