Scotland is forecast to have the best conditions for the rest of the Easter weekend, while the dry start comes to an abrupt end in southern parts of Britain.
Temperatures were up to about 17C in Glasgow and parts of the Highlands on Saturday afternoon, hotter than in most of England.
And the warm weather is likely to continue, with forecasts of sunshine across much of Scotland on Sunday.
Heavy showers and thunder are expected south of the border as rain spreads from the south east of England across central areas and Wales by tomorrow afternoon.
It could mean a washout for many people planning outdoor Easter Sunday celebrations after most of the UK has enjoyed a recent spell of warm weather in April.
MeteoGroup forecaster Chris Burton said: “It will stay dry and fine on Sunday across Scotland, Northern Ireland, northern England and the far north of Wales.
“But it’s going downhill across southern areas of the country.
“There will be showers spreading northwards from the south east of England. It will be quite heavy across southern and central areas and we may see some thunder.
“On Monday, Scotland escapes the worst but it will be fairly cloudy across the rest of the country with showery outbreaks.
“Scotland is getting the best of the weather for the rest of the Bank Holiday weekend.”
Temperatures across the rest of the UK are expected to range from 11 to 15C, while on Monday, it could rise to 18C in places, Mr Burton said.