Increased cloud coverage in the coming days is expected result in showers and some isolated storms inland and in the mountains, the met office said on Tuesday.
On Wednesday, though it will be mainly fine, there will be increased cloud coverage initially in the western and northern coastal areas.
This is likely to develop into rain and storms in some areas, the met office said.
Temperatures Wednesday are expected to fall below the seasonal average.
Thursday and Friday could see the same weather patterns.