Heavy showers and thunderstorms are expected to develop on Wednesday and may cause some flooding and travel disruption.
Where they do develop they could be slow-moving and persistent with as much as 20-25 mm of rain falling within an hour and possibly 40 mm in 2-3 hours in a few places. Lightning and hail will be additional hazards.
What to expect
- Probably some damage to a few buildings and structures from lightning strikes
- There is a good chance driving conditions will be affected by spray, standing water and/or hail, leading to longer journey times by car and bus
- Delays to train services are possible
- Some short term loss of power and other services is likely
Regions and local authorities affected in Wales
- Blaenau Gwent
- Merthyr Tydfil
- Neath Port Talbot
- Rhondda Cynon Taf
- Vale of Glamorgan