WEEKS of blue skies and sunshine will be rudely interrupted by dark clouds and thunderstorms tomorrow.

The Met Office has released a yellow weather warning for storms across the south-west of England and all of Wales.

The warning lasts from 11am to 8pm, though there is a 30 per cent chance of rain from 9am and a 60 per cent chance of thunderstorms from 10am to 1pm.

A 30 to 50 per cent chance of rain is predicted throughout the rest of the day until the weather warning ends.

A spokesperson for the Met Office said: "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 focussed into slow-moving bands, particularly over southwest England, with some locations receiving around 20mm in an hour.

"Some flooding of a few homes and businesses is likely, perhaps leading to some damage to buildings.

"There is a good chance driving conditions will at times be affected by spray and standing water, leading to some minor journey delays.

"Some short term loss of power and other services due to lightning strikes is possible."

Temperatures will vary from 14 to 23C and are expected to stay at 20C during the thunder and lightning.

Despite the showers, visibility should still be good during the day.

After the downpours clear, sunny skies will return just in time for the weekend and temperatures will rise slightly to 25C.

However, the rain could dampen spirits at the Royal International Air Tattoo, which kicks off on Friday.

The country's biggest air show attracts tens of thousands of visitors from all over the world, with this year's event set to include a celebration of the RAF's 100th anniversary.

In 2008, one day of RIAT had to be cancelled for the first time ever after three days of heavy downpours left the fields waterlogged.

At the moment, the weather is not expected to affect the air show and history shouldn't repeat itself, but this could change.

A spokesperson for RIAT said: "No decisions will be made until later today, when the forecast is firmed up."