Laois is the among the counties which will be impacted.
Met Éireann has issued a status yellow warning for rain for the southern half of the country from tomorrow evening.
It affects Laois, Carlow, Kilkenny, Wexford and Munster.
The alert begins at 6 o'clock tomorrow evening and will run until the early hours of Friday morning.
Met Éireann says persistent showers may cause localised flooding.