Thunderstorms and torrential downpours will hit England and Wales on Wednesday and Thursday, but warm weather is likely to continue for the rest of the week.
Some areas could see as much as a month’s rainfall in a few hours on Thursday which could cause flooding, the Met Office warned.
Yellow warnings for thunderstorms have been issued for today and tomorrow and the Met Office said it is likely further alerts may be issued at short notice ahead of the most intense thunderstorm activity.
Dan Holley, deputy chief forecaster at the Met Office, said: “The most intense impacts are likely to be focussed on central, southern and south-east areas of England. Here some locations will witness torrential downpours, large hail and frequent lightning.”
Spray and sudden flooding could lead to difficult driving conditions and some road closures, the Met Office said. It added that fast flowing or deep floodwater causing a danger to life is also possible.
The break in weather follows the hottest day of the year on Tuesday when temperatures soared to 32°C at Kew Gardens and Heathrow.
Temperatures will remain high at 30°C or above into Wednesday and Thursday, with thunderstorms expected in the South East on Wednesday and across much of England on Thursday.
Met Office meteorologist Becky Mitchell said: “The heat and humidity we’ve got across England and Wales is going to spark off some thundery showers on Wednesday and Thursday so we’ve got some yellow weather warnings in force.”
There is a risk of flooding on Thursday afternoon in some parts of the country, but the thunderstorms will be “quite hit and miss”.
The yellow weather warnings for thunderstorms are in place across the South East on Wednesday, spreading up through the North to cover the entire of England on Thursday.
The Met Office said Thursday afternoon could see 50 to 100mm of rain in a few hours in some spots, which is more than a month’s worth of rainfall.
In Scotland, temperatures will reach highs of 21°C on Wednesday amid sunny intervals, and 23°C on Thursday after spells of rain and cloud in the morning.
Northern Ireland will mirror much of Scotland’s conditions, with slightly cooler highs of 20°C expected on Wednesday.
The heat is not set to last into next weekend as temperatures are expected to return to the mid-20s in the south as a band of rain moves through the country on Saturday.
To cope with warm evenings, the Met Office has urged Britons to keep their homes as cool as possible.
It said: “Overnight temperatures are going to be very high so it’s quite hard to cool houses down in that situation because you don’t have the relief overnight and temperatures dropping.
“If you can open your windows at night, try to let some of the cooler air in and keep curtains or blinds shut during the day”.
