Warnings of thunderstorms and heavy rain remain after scorching temperatures were recorded for the sixth day in a row in parts of the South East.
A yellow storm warning covers much of England and Wales due to unsettled conditions caused by the heatwave. On Wednesday evening heavy rain left parts of London underwater.
It comes as water firms advised customers in certain areas to restrict their water usage amid sweltering conditions.
Thames Water said that ongoing power supply issues in Guildford meant it was using tankers to bring water into the area, as it urged customers to use water for essential purposes only in the coming days.
Essex and Suffolk Water said that due to “record water demand” it was working to maintain supplies but users could notice lower than normal pressure.
Temperatures reached 34.6C in St James’s Park in central London on Wednesday, marking the first time since at least 1961 that there had been six consecutive days of 34C and above.
It was also the third day in a row of the mercury hitting 35C or above, with Wednesday’s highest temperature of 35.4C recorded at Heathrow, according to the Met Office.
Forecaster Greg Dewhurst said: “It’s not often we get temperatures this high over several days, and that is triggering thunderstorms across parts of England and Wales.
“If rain is falling on places that have been quite hot and dry, and the ground is quite hard, the rain doesn’t have anywhere to go, and from that we can see flash flooding.