Travel disruption and damage to buildings are expected when Storm Austen, the first named storm of the autumn, hits south Wales later this week.
The Met Office said the storm will bring a spell of strong winds up to 70mph (112km/h) overnight on Thursday and into Friday, mainly in coastal areas.
The yellow warning, external for Wales was issued on Wednesday morning, with periods of heavy rain also expected. The Met Office said injuries and danger to life from flying debris are possible.
Some roads and bridges may close, and longer journey times and cancellations to public transport are possible.
The weather warning is in place between 00:00 and 14:00 BST on Friday.
