Met Éireann has issued a Status Yellow weather warning, with heavy overnight rain forecast over the midlands and west of the country.
The alert came into effect at 9pm tonight and is valid until 12pm tomorrow.
Met Éireann says spot flooding is expected, and the rain may turn to snow in some areas for a time.
The weather warning is for Connacht, Longford, Offaly, Westmeath, Cavan, Monaghan, Clare, Cork, Kerry, Limerick and Tipperary.
Updated Warning: Status Yellow rainfall warning issued for Connacht, Longford, Offaly, Westmeath, Cavan, Monaghan, Clare, Cork, Kerry, Limerick and Tipperary.— Met Éireann (@MetEireann) March 15, 2019
Valid from 21:00 hours Fri, 15-Mar-2019 to 12:00 hours Sat, 16-Mar-2019 pic.twitter.com/t1Na5ccawr
Separately, a Status Yellow snow-ice warning has been issued for Donegal.
Met Éireann says that heavy rain will turn to snow tonight and tomorrow morning, which will lead to poor driving conditions.
The alert is valid from midnight until 12pm tomorrow.