The UK was struck by lightning between 15,000 and 20,000 times as the "mother of all thunderstorms" rolled across southern England overnight, meteorologists said.
The London Fire Brigade said it had taken more than 500 weather-related calls as the warm and humid bank holiday weather broke down into an "utterly intense" storm.
In Warwickshire, the fire service said five properties were struck by lightning in the early hours of Sunday, while in Dawlish, Devon, a telephone box burst into flames after a BT pole was hit on Saturday evening.
Western Power Distribution said nearly 1,000 properties had been left without power across the Midlands, with the majority of outages down to lightning.
A cluster of 17 flood alerts has been issued for parts of the Thames Valley, while West Midlands and Bedfordshire fire services warned motorists of the risks of driving on flood-hit roads.
Disruption continued into Sunday, as many complained that planes were delayed at Stansted Airport.
Storm over the City
Met Office meteorologist Charlie Powell said information suggested there were "somewhere between 15,000 and 20,000 strikes across the UK during the overnight period".
He explained: "Temperatures overnight did not fall much below 15 or 16 degrees, for the end of May that's a pretty hot and humid night so everything was primed.
Morning!— BBC Weather (@bbcweather) May 27, 2018
Did you sleep well?
Possibly not if you were in the south of the UK. Around 50,000 flashes of lightning recorded across central and southern England, Wales and around the English Channel overnight ��️��
"We had some storms coming in from northern France and some building up in the Channel and they sort of spread out and have been working their way in.
"It looks like there just one huge area of thundery showers that worked across London just before midnight."
The LFB said it had taken 505 weather-related calls overnight, although the majority were down to flooding and no fires were reported to have been started by lighting strikes.
Torrential rain at Kew Gardens, in south-west London, saw more than half an inch of rain fall in an hour.
A Met Office warning of heavy thunderstorms is in place until 6am on Monday, covering much of England and all of Wales.
Overnight, as the warm and humid Bank Holiday weather broke down into the "utterly intense" storm, many on social media shared stunning images of famous landmarks lit by flashes of electricity.
BBC weather presenter Tomasz Schafernaker tweeted excitedly:
Mother of all #thunderstorms now over London. Oh boy! This UTTERLY INSANE. I’ve never seen a storm with such frequent lightning in my life I don’t think. Mostly sheet lightning and not too loud but flashes are spectacular. pic.twitter.com/b3RjiD8Nf2— Tomasz Schafernaker (@Schafernaker) May 26, 2018
Photographer and journalist Andrew Lanxon Hoyle shared an image of the Suleymaniye Mosque in Dalston, east London, lit from behind by a brilliant fork of lightning, tweeting: "The lightning storm over London right now is utterly INTENSE."
Lightning strike causes chaos at Stansted
People at Stansted airport faced hours of delays on Sunday morning after a lightning strike hit the airport fuelling system.
This meant planes were unable to refuel as engineers worked to fix the issue.
Many complained of the crowds, chaos and lack of information.
One passenger said he had been waiting on a plane for two and a half hours, tweeting: "Stansted airport ground to a halt due to fuel issues. Hour delay already captain says could be hours before resolved.
"2.1/2 hours sitting on the plane and no communication for an hour unbelievable."
John Mann MP was among those caught up in the disruption. He tweeted: "Nothing leaving Stansted this morning- fuel depot hit by lightening apparently. Tankers on their way. Empty skies."
@STN_Airport@Ryanair#understaffed on a busy day, causing huge #delays at checkin & security. Passengers rushed to board their flights to find that a lightning strike had taken out the fuel system & all flights are delayed. No warnings on dep. boards & you knew it. #Stanstedpic.twitter.com/FcJo7z8p6c— Andy Murphy (@andymurphy73) May 27, 2018
Stansted said in a statement: "Due to an earlier lightning strike, the aircraft fuelling system was unavailable for a period this morning. Engineers have been on site and have now restored the system, however flights may still be subject to diversion, delay or cancellation.
"We apologise for the inconvenience and advise all passengers to check with their airlines for their latest flight updates."
A 'reverse arch' over Wembley Stadium
South of the river
Pamelasaurusrex shared a photo on Instagram of two people running for shelter outside King's Cross Station as a lightning bolt arced across the sky over nearby St Pancras.
Samuel Wilkinson captured the split-second lightning shot toward the earth with The Shard skyscraper below, while the RNLI at Tower Bridge shared a photo of the view over the South Bank as the sky lit up.