PARTS of the country are bracing themselves for flash flooding after forecasters predicted heavy rain and thunderstorms in the wake of the heatwave.

The Environment Agency and Met Office have warned of localised flooding in London, the south east and eastern England, saying up to 40mm of rain could fall in the space of a few hours.

And there is a flood alert for rivers in Lewisham, Bromley, Greenwich and Croydon boroughs with up to 30mm of rain predicted.

Surface water flooding could also occur in other regions hit by heavy storms.

Hail storms are also expected as the weather makes an abrupt U-turn following the hottest day of the year so far yesterday.

The threat of heavy rain comes after temperatures soared in a heatwave that saw the mercury reach 32.8C in Gravesend, Kent, in the hottest day of the year so far.

An Environment Agency spokesman said: "Environment agency staff are on 24-hour alert and teams are monitoring river levels as the band of rain moves across the country.

“The public is encouraged to tune in to local media for weather forecasts for their area and to keep an eye out for signs of surface water flooding."

A Met Office spokesman said the "sheer volume of rainfall falling in such a short space of time" in some areas could lead to surface water flooding in some places.

But the extremely dry spring, which has left some parts of east and central England officially in a state of drought, means that most rivers are at low levels and are unlikely to flood.

According to MeteoGroup, the weather division of the Press Association, showers and thunderstorms are expected in south east England and East Anglia.

Temperatures in London are not forecast to climb higher than 23C, while the west and the north will even see the weather turn chilly.

Tom Tobler, a forecaster at MeteoGroup, said: "There will be heavy showers and thunder storms developing in South East England and East Anglia during the morning. There will be a risk of localised flash flooding but during the afternoon and evening the storms should clear eastwards.”