The warning is valid from 8pm today (Friday). It is predicted there will be frequent lightning, possible large hail and gusty winds. There is also a chance of torrential rainfall.
Up to 25 to 35mm of rainfall could fall in areas and much of this could fall within an hour. Some locations may experience torrential rainfall, seeing 30-50mm within a few hours.
The Met Office has warned there is a chance floods or lightning strikes may occur, causing damage to buildings and a small chance that travel may become delayed.
This yellow warning stretches across a large area, covering the south of England, and reaching south Wales and the Midlands early on Saturday.
The worst of the weather is expected to ease on Monday.