A Yellow warning is in place for the whole of Scotland, the North of England, and Northern Ireland, from 1pm on Saturday until the early hours of Sunday morning.
Temperatures across the country had soared throughout Thursday and today, with temperatures in the high twenties recorded.
But that tropical weather comes with a downside, as an area of high pressure causing the mini-heatwave was set to be followed with thunderstorms and torrential rain.
The Met Office warning for the weekend says: “Heavy, thundery showers on Saturday afternoon and evening have the potential to bring localised flooding, hail and frequent lightning.”
“Rising temperatures will cause heavy showers to develop. Whilst many will miss the worst, some places could see 20-30 mm in an hour or less. The risk of this looks slightly higher across Scotland than across England or Northern Ireland.”
The thunderstorms and torrential rain could make for difficult conditions at the Scottish Cup Final at Hampden between Celtic and Aberdeen, which takes place in the middle of the projected downpour.