Met Éireann has issued a Status Yellow rain warning for counties Cork, Waterford and Wexford.
The national forecaster said that from 3:00p.m today (Thursday, July 29) until 5:00a.m on Friday, heavy or thundery showery rain can be expected with the risk of spot flooding.
For the rest of the country, it will be mostly cloudy today with patchy outbreaks of rain in the north this morning.
It will be generally drier further south, with well-scattered showers and a few hazy sunny spells.
However, a band of rain will move into the southwest this morning, reaching much of Munster by this afternoon and extending across south Leinster this evening, turning heavy at times in the south and southeast.
There will be highs of 16° to 19°, in a light to moderate northwesterly breeze.
There will be rain lingering in the east and southeast for much of tonight, clearing towards dawn.
It will be mostly dry early tonight through the middle of the country but showers in the north and west will move eastwards to remaining areas overnight.
There will be lows of 9° to 13° degrees, in a light to moderate westerly breeze.
Tomorrow (Friday) will be showery in most areas with some heavy downpours, though the showers will be fewer over Ulster.
There will be some brighter spells but generally a lot of cloud.
On Friday night, showers will become confined to Atlantic coasts and the southwest early in the night with some mist and fog patches developing, in a light westerly breeze.
Overall, Met Éireann says the weather will be mostly dry over the August Bank Holiday weekend. It is expected to be cloudy but with some warm sunshine at times.