Rain weather warning before Christmas for London, Hertfordshire, Essex

A yellow warning for rain has been issued for much of the south of the country, including Hertfordshire, London and Essex.

And it will run from 6am on Wednesday, December 23, to 6am on Christmas Eve.

The heavy rainfall could lead to flooding in some places and make it difficult for those travelling to shops to prepare for the festive season.

Due to Tier 4 restrictions in London and surrounding areas and the tightened Christmas rules, many people will not be allowed to travel to other households during the time weather warning is in place.

The weather service said there is a "small chance" that flooding could damage homes and businesses and cause hazardous conditions, and a "slight chance" of delays or cancellations to train and bus services.

A yellow warning for rain covering much of the south of the UK. Photo: Met Office

A yellow warning for rain covering much of the south of the UK. Photo: Met Office

There is also a "small chance" that some communities become cut off by flooded roads.

The Met Office warned: "Spells of heavy rain are expected across southern England and parts of south Wales during Wednesday and into early Thursday.

"The heaviest rain is likely to develop during Wednesday evening and continue overnight before clearing away to the southeast by Thursday morning.

"Much of the area is likely to see 20-40 mm through this period. There is still some uncertainty in exactly where the heaviest rain will fall but there is the potential for some places to see as much as 50-70 mm of rain.

"The heavy rain will be accompanied by strong north to northeasterly winds during Wednesday evening and overnight."

Light rain has also been forecast for later this afternoon and evening for the areas in and around London.