A large area of low pressure crossing the UK has already brought areas of heavy and thundery rain to many northern and some western parts of the UK over the last few days.
More thunderstorms are expected in parts of north-east Scotland later on Wednesday.
The Met Office has issued a yellow warning between 10:00 and 21:00 BST. It warns of heavy, slow-moving showers and some thunderstorms breaking out from late morning.
Along with lightning, gusty winds and some hail, the storms will have the potential to produce up to 50mm of rain in a few places over three to six hours. This could lead to localised flash flooding and impact the transport network.
Later on in the day and into the night, unseasonably blustery winds will develop across parts of Scotland, Northern Ireland, the Isle of Man and northern England. Gales are possible on some hills and coasts.