The Met Office has issued an amber warning for rain in the capital, with torrential downpours expected across the south east of England. More thunderstorms are forecast, with frequent lightning, large hail and strong gusts of wind are being forecast.
The public is being warned to prepare for possible localised flooding, both from surface water as well as from watercourses, as the downpours intensify from 3pm.
There is still, however, a "yellow" warning of a heatwave for the UK today, advising people to be "alert and ready". The Met Office said there was a 60% chance of a heatwave continuing until tomorrow morning, with high levels of humidity.
Today: Hot and humid with some sunny spells but also with the risk of further thundery rain or thunderstorms with some torrential downpours and local hail likely. Maximum Temperature 30C.
Tonight: Remaining warm and humid overnight with further thundery showers or thunderstorms likely at first, but becoming mostly dry and rather cloudy at times later in the night. Minimum Temperature 17C.
Sunday: Mostly dry at first with some sunny spells, but locally heavy and thundery showers are likely to develop by the afternoon. Remaining very warm but a little less humid. Maximum Temperature 26C.
Outlook for Monday to Wednesday: Some bright or sunny spells but scattered showers are still likely to develop during the day. Staying generally very warm or hot but cooler near the coast.