[B]outs of rain, heavy and thundery at times, will move in from the west to affect parts of southern Scotland and northern England from the early hours of Wednesday.
More extensive thunderstorms may then break out over a larger part of England and Wales from late Wednesday afternoon onwards into Wednesday night, leading to torrential downpours, frequent lightning and a chance of hail.
Rain over northern England early on Wednesday may locally lead to 20 mm or 30 mm of rain falling in one or two hours
This could result in some disruption, more likely from late Wednesday afternoon, which may include sudden localised flooding of transport routes, homes and businesses.
Frequent lightning in association with the heaviest rain may also temporarily disrupt power supplies.
However, many places will likely see little or no impacts.
Indeed many parts of the warning area will see dry and sunny weather through much of the daytime on Wednesday.