Flood alerts have been issued for Christchurch Harbour as a downpour of rain is expected following days of blistering heat.

Forecasters are predicting thunder, lightning and flooding as a yellow weather warning comes into force across the UK.

The Met Office has implemented the warning for Scotland and Northern Ireland until 11.59pm on Monday and 11.59pm for all of England and Wales on Tuesday after a change in air pressure led to dramatic showers.

Power cuts and delays and cancellations in trains and buses are predicted, while spray and sudden flooding could lead to difficult driving conditions for motorists.

Greg Dewhurst, a meteorologist at the Met Office, said the week would start off quite humid before cooling down later on.

He told the PA news agency: “We’ll start off initially quite humid, particularly across the south and the east of the UK, with thundery showers and sunny spells, but it will gradually become cooler and fresher as the week goes on.

“First half of the week, we’re looking at some heavy downpours and thunderstorms developing.”

Flood alerts in BCP

A flood alert has been issued for Christchurch Harbour by the Environment Agency with the rain set to arrive today.

They said: "The Flood Alert will be in force for 2 hours before and after this high water time. Forecast tide levels are 1.20m with wind direction and speed being South Westerly, Force 3 respectively.

"Forecast high Spring tides will raise water levels in the harbour. This is expected to result in standing water affecting footpaths and low lying land on the seaward side of flood defences."

The alert will be updated at midday on Monday.