An amber warning for extreme heat has been extended but the record-breaking hot spell is coming to a close.
The Met Office warning covering the East and South East now runs until 9am on Sunday.
Heat records were broken on three consecutive days from Wednesday, reaching a provisional peak of 37.3C in Santon Downham in Suffolk on Friday, and Saturday saw a high of 32.3C in the same location.
The day’s heat and humidity has caused thunderstorms to develop, and a yellow thunderstorm warning is active until 11pm on Saturday.
It says frequent lightning, large hail, gusty winds and brief heavy downpours are possible in central and eastern parts of England.
Thunderstorms have already hit the UK and the weather disrupted flights on Saturday.
A total of 484 inbound and outbound flights were delayed across Gatwick and Heathrow airports by the evening, according to the FlightAware tracker.
Heathrow had 42% of its flights delayed and Gatwick 50%, it said.
Meanwhile, early on Saturday morning, Kent Fire and Rescue Service were responding to three house fires caused by lightning strikes.
The thunderstorms forecast on Saturday evening will move rapidly north-eastwards before clearing above the North Sea.
The Met Office warning said short term loss of power is possible and damage to vulnerable structures.
High temperatures are clinging on in East Anglia and some face another tropical night that will not drop below 20C on Saturday.
However, temperatures are expected to drop by around 5C or 6C the following day.
This will produce highs of 25C to 26C on the eastern coast and around the mid-to-low 20Cs elsewhere.
Humidity levels will also fall to give “a much fresher feel than what we saw for the latter part of last week”, Met Office meteorologist Liam Eslik said.
The heatwave smashed the long-standing record for June heat, which dates back to the summer of 1976, by more than 1C, which is significant given such records were usually broken only by a fraction of a degree in the past.
A total of six people drowned during the heatwave and there were 15 water-related fatalities in May.
Scientists warned that the heatwave would have been virtually impossible 50 years ago, with human-driven climate change fuelling more intense and frequent extreme heat events.
Health chiefs warned of the impact the conditions were having on services this week as they faced significantly more life-threatening emergency calls.
Hundreds of schools and nurseries were forced to close and a hosepipe ban was brought in for Kent amid surging demand.
Several hospitals declared critical incidents, with University Hospital Southampton forced to cancel a number of planned operations and some outpatient appointments.
The heatwave was driven by a “heat-dome” – an area of high pressure that stalls over a region and traps heat – settling over western Europe and bringing extreme conditions across the continent.
This has been compounded by human-driven climate change, mostly caused by burning fossil fuels, which is making such extreme heatwaves more frequent and intense.
