A thunderstorm warning has come into effect for southern England as downpours continue across parts of the UK.

The yellow weather warning for thunderstorms began at 5am and runs until midday on Tuesday.

The Met Office said 15-20mm of rain could hit the affected area, which includes London, the south east and the south west of England

Some buildings could be damaged by lightning strikes or strong, gusty winds – while short power cuts are also considered “likely”.

Drivers and those thinking of taking a bus should expect their journeys to be longer due to spray, standing water and hail.

Trains and planes may also be delayed due to adverse weather conditions.

On Tuesday morning, the Environment Agency had 11 flood warnings in place, meaning flooding is expected, with 120 lesser flood alerts also active.

Areas of concern include the River Severn in Gloucester and the River Eden in Cumbria.

Met Office meteorologist Marco Petagna said Storm Debi is expected to clear away from the UK to the east in the early hours of Tuesday, but “wet and windy weather” should linger.

He said on Monday: “Tomorrow morning you will see heavy and potentially thundery showers moving eastwards across the south of England.

“We could see 15-20mm, almost an inch, of rain across some southern counties of England combined with fairly gusty winds as well.

“A week’s worth of rain could fall in an hour or two in that warning area and you could see wind speeds of 40-50mph.

“If you are in that warning area, it is going to be quite tricky (to travel).

“Allow extra time to travel and keep tuned to the forecast overnight.

“If you are out and about, take extra care and be prepared to see thundery showers.”

A “very active” jet stream has been the cause of much of the wet weather, Mr Petagna said, as he warned it shows “no sign” of stopping in the next week.

He said: “The active jet stream is helping to move a deep area of low pressure. It is quite a long way south and much of the UK is in the firing line.

“The next week or so will still be pretty unsettled, with some brighter spells but not for long.”

Despite the wet weather, fairly normal temperatures for this time of year of 9-12C are expected.

The warnings come as Storm Debi caused 70mph gusts on Monday, leading to flight cancellations.

British Airways said that, like other airlines, it had to “make a small number of cancellations” due to the bad weather which has reduced the number of flights air traffic controllers will allow to land per hour.

A spokesperson said: “We’ve apologised to our customers for the disruption to their travel plans and our teams are working hard to get them on their way as quickly as possible.”