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 warned that up to 30mm (1.2in) of rain could fall in an hour in some areas.
The agency says that almost every county in England and Wales is at "medium" risk of flooding today, and has issued 59 flood alerts at the time of writing, warning people to be prepared.
The majority of these are in the Midlands, the South East and the South West.
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.