After a record-breaking spring, the weather has been distinctly unsettled since the start of June with wetter, windier and cooler temperatures than are typical for the start of meteorological summer.
On average, England experienced just 32.8mm of rain last month in what was its driest spring in more than 100 years.
Now, it appears, there could be more rainfall on Saturday than there was in the whole of May in some places.
It can be hard to predict where thunderstorms will turn up because they are small-scale weather features.
Not everywhere will get a torrential downpour or a thunderstorm – most parts will see a shower but some may stay dry and avoid the rain completely.
The weather agency has warned that in places that do experience heavy showers there is the potential for disruption to transport, with driving conditions affected by spray and standing water, leading to longer journey times. Train services could also be delayed.
It also said that some short-term loss of power and other services was likely, and potential lightning strikes could cause damage to buildings.
While the storms are expected to occur for much of the day, they will ease off in the west from mid-afternoon.
Thunderstorms are also possible outside the warning area, with parts of Yorkshire, Lincolnshire and parts of south-east Scotland likely to experience a few this afternoon.
