Thunderstorms are moving across parts of the UK, after some areas saw the longest stretch of high temperatures since the 1960s, according to the BBC.
Yellow storm warnings apply to much of England, Wales, parts of Northern Ireland and south-west Scotland following highs of more than 30C.
There is a small chance of flooding, travel disruption and power cuts in those regions, the Met Office said.
It comes after torrential rain and lightning lashed parts of Scotland.
The yellow warning applies to Wales and the majority of England until Monday night next week, and forecasters have warned of potential damage to buildings from lightning strikes or strong winds.
As of 15:00 BST, the Met Office said thunderstorms had broken out across the southern counties of England between Devon and Kent, with frequent lightning, heavy downpours, large hail and gusty winds possible in the coming hours.
Earlier, it reported thunderstorms had moved across the southern Midlands, East Anglia and north-west London.
BBC Weather has predicted highs of 29C in the south-east of England on Thursday, with cooler temperatures expected in Scotland and the north-east of England.
Skies across the UK were lit up by lightning as thunderstorms hit on Wednesday evening, following a week of hot weather.
Lightning struck a house in Wrexham, blowing out power sockets and setting fire to a curtain.
Fire crews were also called to deal with flooding incidents around Wrexham, as well as other parts of Wales including Denbighshire and Powys.
Several other places have recorded heavy downpours over the past 24 hours, such as Gnosall, West Midlands, which recorded 103.8mm of rain – over a month’s worth – in one night, according to BBC Weather.
The Met Office has warned the high temperatures triggering the thunderstorms could cause flooding.
“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,” Met Office forecaster Greg Dewhurst said.
“It’s still going to be warm and humid and that could then trigger some thunderstorms across parts of England and Wales through the afternoon and evening [on Thursday],” he added.
“Generally, the rest of the week remains unsettled with showers, some of them thundery and heavy, but there will still be some warm, sunny spells at times too.”
“It’s not often we get temperatures this high over several days, and that is triggering thunderstorms across parts of England and Wales.”