Thunderstorms are set to break up the long spell of sweltering hot and dry weather in parts of the UK.

The Met Office has issued a yellow weather warning for 11am to 8pm on Friday, putting regions such as London and south-east England, the North West, South West, Wales and the West Midlands on notice of a risk of downpours.

It is only the second thunderstorm warning to be issued since the new alert was introduced last month and it states that heavy showers in some places could bring “around 20mm (0.8in) in an hour”, while others will remain dry.

Met Office meteorologist Martin Bowles said the areas which could be heaviest hit include Wales and central southern England.

“You can get a lot of rain in a short time. You can get flooding issues with people driving on roads facing large puddles,” he said.

“It is a be prepared warning, so it is not expected to cause problems but people need to be aware of it.”

The warning states: “Heavy showers, which will most likely become thundery in places, are expected to develop quite widely across parts of England and Wales later Friday morning and through the afternoon.

“Some of the showers are likely to become focused into slow-moving bands, particularly over south-west England, with some locations receiving around 20mm in an hour.

“As is the nature of showers however, many places within the warning area will miss them altogether, and have a dry day.”

Despite the downpours, which could see some lightning strikes, many people across the country will still be able to enjoy a very warm 27C-28C summer day.

Anyone in a thunderstorm area and further east could see the temperature drop to around 20C.