Torrential rain, thunder and lightning is blighting the first weekend of the school holidays, as thousands set off across the UK for their summer break.
The heavy downpours have already caused flash-flooding in the South East and the Midlands, with more expected Sunday as the rain spreads north and west.
In just four hours on Saturday evening Market Bosworth in Leicestershire endured 61mm of rain and many other areas saw between 20mm and 30mm, with similar amounts forecast on Sunday.
This compares with an average rainfall of around 80mm for the whole month of July, weather experts said.
The Met Office has increased its weather warning level to "amber", the second of three levels, urging residents in the Midlands and north of England to be prepared for storms likely to cause surface water flooding and disruption today.
The Environment Agency has also issued 32 flood alerts in the same areas, and two more serious flood warnings near Rochdale and Sheffield as river levels rise.
But forecaster Tom Tobler, from MeteoGroup, the weather division of the Press Association, said there is a chance of being hit by heavy downpours almost anywhere in the UK today.
He said: "The torrential rain and thunderstorms will move into north England and into Scotland, as well as across to the South West and South Wales.
"Between 20mm and 30mm could fall, some of it on top of areas which might have already seen showers, so there is a continued risk of flash-flooding.
"But you could catch a heavy shower pretty much anywhere in England and Wales, but the South East should remain mainly dry and up to 25C."
It comes after a glorious run of baking sunshine in July which has turned increasingly unsettled over the last week.
The weather is likely to remain changeable over the next few days.