Torrential thundery downpours are set to descend on Britain over the bank holiday weekend, bringing an end to the spell of summery weather.
The UK enjoyed the hottest day of the year so far on Friday as temperatures peaked at 29.4C (85F) in Lossiemouth, north Scotland, the Met Office said.
For the third consecutive day each of the home nations enjoyed the warmest day of the year and most parts of the country saw temperatures above 25C (77F).
The mercury hit 28.9C (84F) in Porthmadog, Wales, 28.6C (83F) in Blackpool, England, and 26.2C (79F) in Castlederg, Northern Ireland.
But temperatures will dip as showers move in across the country over the long weekend.
Met Office forecaster Luke Miall said: "It was a very warm summer's day for most. The satellite imagery had pretty much no cloud across the UK today.
"But there are some changes on the horizon."
The worst of the wet weather on Saturday is forecast in the north of the country, where a yellow weather warning for rain is in place.
"Through tomorrow, the heaviest and most frequent showers are likely to be across northern England, Northern Ireland and Scotland," Mr Miall said.
"Here we will see some really quite torrential downpours. There could be frequent lightning, heavy rain, the risk of hail as well within those showers.
"All the while, much fresher conditions are starting to spread."
Around 30mm to 40mm of rain could fall in a short time in these areas, creating a risk of surface flooding, he added.
England and Wales will be largely dry and sunny on Saturday afternoon and temperatures in the mid to high 20s are possible in the east and in north-east Scotland.
But conditions will take a turn for the worse on Sunday and Monday when weather warnings are in place for the south.
"That is again for the potential of some heavy thundery showers spreading through Sunday and Monday across these areas," Mr Miall said.
"Hit and miss in nature, but the risk is there for some really quite lively downpours."
The country will feel "fresher" by the end of the weekend, with temperatures widely expected to be in the late teens and early 20s.