"There is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds".
Hot temperatures in England have created the flawless conditions for the severe stormy weather which is set to cause travel chaos this weekend.
Met Office chief meteorologist Frank Saunders said: "Up until Monday, thunderstorm warnings cover much of England and Wales, with parts of southern England and South Wales seeing the greatest likelihood of impacts".
The Met Office has issued a storm warning across the United Kingdom for the next five days.
Devon and Somerset Fire and Rescue Service said on Twitter it had received numerous calls relating to flooding in properties in Devon, with some residents reporting up to 18 inches of water inside their properties.
Drivers were caught by flash flooding following "biblical rain and hail" on the M25, as one onlooker said that more than 20 cars looked as if they were stranded and that the water was feet-high in some areas.
Some 10 flood alerts covering areas in the West Midlands were issued by the Environment Agency on Wednesday evening, alongside three flood warnings - meaning immediate action is required. Biblical rain and hail.
Temperatures were cooler compared to the rest of the week, with the mercury reaching 29.6°C (85.3°F) in the village of Frittenden in Kent, according to forecaster Mr Box.
Torrential downpours also brought road closures and widespread flooding across parts of the West Midlands, in particular.
But the heatwave in southern England is set to continue, with London and the South East expecting temperatures of up to 36C (96.8F) on Wednesday.
Yellow thunderstorm warnings are in place for most of England and Wales for the next five days.
But in the south and west the sun will continue to bring warm temperatures and humid heat.
This month the United Kingdom has experienced five tropical nights and six continuous days of heatwave weather.