Thunderstorms and torrential rain have swept across parts of southern Britain, with frequent lightning flashing across the sky.
Around 15,000 lightning strikes were recorded in four hours on Saturday night, BBC Weather said.
Thunderstorms moved northwards across the south of England, the Midlands and Wales, and are expected to continue throughout Sunday.
The Met Office has issued a yellow warning for heavy rain and flooding.
On Sunday morning, storms brought more than an inch of rain to parts of Wales and the Midlands in just an hour.
Parts of Wales and central and southern England could see further thunderstorms on both Sunday and Monday, with the Met Office warning of the possibility of power cuts and delays to trains and buses.
Many people got out their cameras to photograph and video Saturday night's electrical storm, which was called "utterly insane" and "like being under a strobe light".
Others remarked that they had "never seen a storm quite like this" and said the flashes were "stunning".
BBC Weather presenter Tomasz Schafernaker called it the "mother of all thunderstorms" as he watched it over London.
"Oh boy! This [is] utterly insane," he said.
"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."
Forecaster Gemma Plumb, from BBC Weather, said as the storms push northwards across England throughout Sunday, more are coming up over the English Channel from the continent.
The Met Office weather warning for rain is in force until 6:00 BST on Monday and covers all of Wales as well as southern and central England.
Flooding of homes and businesses could happen quickly, the Met Office said. It added that fast-flowing or deep floodwater is possible with damage to some buildings from flooding, lightning strikes, hail or strong winds.
It comes after a warm Bank Holiday Saturday, with a top temperature of 27.3C in Hurn, Dorset.