Friday’s warning applies to most of south-west England, parts of Wales, the Midlands and west London and is in effect from 12pm to 8pm.

The second warning is in effect all day Saturday from 1am and covers all of Wales and the south-west of England, the Midlands and parts of the south-east of England.

Up to 70mm of rain could fall in the worst-affected areas on Saturday, compared with the average September rainfall in southern England and south Wales of around 60-90mm.

Met Office meteorologist Dan Stroud said: “We’re being treated to almost the last of the summer heat, but there’s a bit of a change coming as we head into Friday, and especially the weekend.”

A “gentle drop” in temperatures is expected over the weekend, with highs of 24 degrees Celsius forecast for East Anglia on Saturday, followed by lows of 20 degrees Celsius in the area on Sunday, he added.

He added that “successive periods of rain” and “normal autumn conditions” are expected next week.