“Where these occur 30-50 mm of rain could fall in less than three hours though only a few spots would likely see these totals. Lightning may also be a hazard during the day.”
On Thursday this becomes more widespread and the warning is in place from 11am until 9pm for East Midlands, East of England, North East of England, North West England, Northern Ireland, South West England, Wales, West Midlands and Yorkshire and Humber.
Of Thursday’s warning Met Office forecasters write: “Following overnight rain and showers, more intense showers and thunderstorms are expected to break out fairly widely from late-morning, before easing during the evening.
“Whilst most areas will miss the most intense storms, torrential downpours are possible in a few places.
“Where these occur, there is potential for 20 to 30 mm of rain in less than an hour and up to 40 mm in two hours.
“This would have the potential to generate surface water flooding, especially if it falls over an urban area.”