After basking in the year's hottest temperatures at the end of the week, Britain is now braced for torrential downpours and storms that could cause flash flooding across large parts of the country.
The Environment Agency has warned almost every county in England and Wales is at "medium" risk of flooding, and has issued dozens of flood alerts, the majority of which are in the Midlands, South West and South East.
One in five flights will be cancelled during a two-hour period at Heathrow today due to thundery weather, the airport has said.
A spokeswoman said: "There is severe weather forecast at Heathrow with a 70% risk of thunderstorms, lightning strikes and hail storms. During thunderstorms the number of aircraft that can take off and land each hour is reduced.
"We have therefore requested that airlines reduce their flight schedule by 20% between 4pm and 6pm. Passengers due to travel on July 19 are urged to check the status of their flight with their airline before travelling to the airport."
Viewers have posted dramatic pictures of the storms which ravaged the UK last night. The photos were posted on the ITV News Facebook page.
It seems thousands of people were woken up by loud claps of thunder, seemingly constant flashes of lightning and torrential rain.
Britain is set to bask in the sunshine in the next few days with health officials issuing guidance on how to stay safe in the sunshine.