Londoners enjoyed the warmest temperatures in the UK on Saturday with highs of 23 degrees.
But, the sunny conditions will be short-lived as the Met Office warned the weather was already starting to turn in some parts of the country by mid-afternoon.
“There’s been quite nice weather around today,” meteorologist Steven Keats said. “But change is already taking place - further north rain is coming into Scotland.”
But, he added that while it will be wet overnight lows on Saturday will be some of the mildest so far with London dropping to 12 degrees and Manchester hovering around 14.
Wetter and cooler weather will sweep south east across the UK on Sunday and Monday.
“It’ll be a bit on the cool side, not desperately cold but not the best weather for a bank holiday,” Mr Keats said.
“On Sunday in the south east it won’t be long before rain pushes down towards you,” he added “But in the west it will turn drier and drier by the afternoon.”
In the south east of England temperatures will still top around 20 or 21 degrees.
On Monday the UK will see a “northwest southeast split of fortunes.”
“Broadly speaking there’ll be sunshine and showers for most of the UK,” he said.
He added that the last day of the bank holiday will be “quite breezy” and while many people will perceive it to be quite wet, the rainfall amount will not be particularly high.
Temperatures will hover around 19 degrees in London, while further north in areas such as Glasgow they are expected to drop to around 13 degrees.