Britons enjoying the current spell of unseasonably warm weather are warned they could face snow after the weekend.
A cold front could sweep the country on Monday, bringing possible sleet or snow, forecasters said.
It comes after much of the UK sweltered in temperatures of above 20C (68F) this week.
Clare Allen, a forecaster with MeteoGroup, the weather division of the Press Association, said: "At the moment, the models look like there will be a cold front clearing southwards across the country after the weekend.
"That will carry rain, and the back edge could turn to sleet or snow. There may be wintry showers behind this cold front, but it should be confined to northern hills, including over the Pennines."
Temperatures on Monday could reach 13C (55.4F) or 14C (57.2F) in London, but may be as low as 8C (46.4F) or 9C (48.2F) in Scotland.
Ms Allen stressed that the picture is still uncertain, but said snow at the beginning of April is not unusual.
The warm weather continued yesterday with a high of 23.3C (73.94F) in Southampton, equalling a previous March 28 record set in 1965.
Today will see high pressure leading to more sunshine in most areas, with temperatures of up to 19C (66.2F) forecast for London - much higher than the average 10C (50F) or 11C (51.8F) for this time of year.
Scotland, north-western areas and Northern Ireland will turn colder overnight and could see drizzle.
Temperatures of 18C (64.4F) are expected in London tomorrow, although it will be cooler in Northern Ireland and north-western areas of Scotland.
Ms Allen said: "Saturday it will be feeling a bit cooler. London will see a maximum of 13C (55.4F), which is still good for this time of year.
"It will generally be cloudy everywhere, with some sunshine breaking through, and patchy drizzle.
"Beyond that we are a bit uncertain. Temperatures could be 12C (53.6F) or 13C (55.4F) in south England and London, Wales and the Midlands on Sunday."