Britons on Tuesday were braced for severe thunderstorms and plummeting temperatures overnight as British forecasters have warned the wet weather could continue into this weekend, bringing the heatwave to an end.

A yellow weather warning is in place until 3 a.m. (BST) on Wednesday covering the east and south east of England, with lightning strikes and heavy rain expected in parts.

"Frequent lightning may occur along with heavy rain -- as much as 20 to 30 mm of rain in an hour in a few places -- large hail and sudden strong gusts of wind," the British Met Office said.

And the wet and windy weather is expected to continue from Thursday until Sunday, Met Office forecaster Marco Petagna told the Evening Standard, a London-based newspaper.

It follows a sweltering day that saw the mercury reach sizzling highs of 33.2 degrees Celsius in Kent on Tuesday.

The forecast has prompted Ryanair to cancel at least 14 departures and 13 arrivals at Stansted Airport.

Petagna said showers have already broken out over the southeastern part of London, which are "likely to become increasingly heavy."

Londoners should also expect thunderstorms throughout the evening, with temperatures dropping to between 16 degrees Celsius and 18 degrees Celsius across the southeastern part of the British capital, he said.

"Tomorrow will be a much fresher day in the south east. It will be generally dry with some sunshine," Petagna said.

He said temperatures across the UK are set to peak around the high teens or low 20s on Wednesday.

The British people have enjoyed weeks of heatwave conditions, with a balmy weekend bringing highs of 30.2 degrees Celsius on Sunday.

It comes amid a sweltering European heatwave, with holidaymakers in Portugal and Spain feeling the brunt of the sun.

Parts of England have spent the equivalent of around two months of 2018 without any recorded rainfall.

The south east clocked up 64 days of zero average rainfall between January and July, while central England had 54 days.

Following the long hot summer, Britain could see warmer-than-average temperatures in the autumn, according to the Met Office.