Thunderstorms and outbreaks of heavy rain already affecting some southern and western parts of the warning area during the early hours of Wednesday then become more widespread through Wednesday daytime.
In a few places these thunderstorms could produce 30 mm of rainfall in an hour and 40 to 50 mm in a few hours. Some parts of the warning area will miss the heaviest rainfall.
What to expect
- There is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds
- There is a small chance of fast flowing or deep floodwater causing dangerous conditions.
- Where flooding or lightning strikes occur, there is a chance of delays and some cancellations to train and bus services
- Spray and sudden flooding could lead to difficult driving conditions and some road closures
- There is a slight chance that power cuts could occur and other services to some homes and businesses could be lost
Where in Wales