The mercury could hit 28C in some parts of England as people round off their three-day weekend - making it the hottest in nearly two decades.
Bank Holiday Monday in 1999 was 23.6C, while the hottest bank holiday weekend ever was in 1995 when temperatures peaked on the Saturday at 28.6C.
But the picture is far less certain for Scotland, where the west faces patchy rain and highs struggling to get above 16C.
Eastern areas like Aberdeen and Edinburgh should fare better with highs of around 21C but the best of the weather is set for southern parts of England.
Met Office forecaster Sophie Yeomans said: “It could beat that (28.6C) for the Monday in which case it would be the hottest ever early Spring bank holiday weekend.”
Most parts of England and Wales will enjoy temperatures in the 20s throughout the weekend, with the best of the weather predicted for the South East.
A weather front in Northern Ireland will keep temperatures low, struggling to get above 16C and some patchy rain is likely, Ms Yeomans said.
She added: “On the whole it looks like a fine and sunny bank holiday for most.”