A Status Yellow rainfall warning has been issued for five counties.
Donegal is forecast to get between 20mm and 30mm of rain from 8pm tonight until 2am tomorrow morning.
In the south, the warning for Wexford, Cork, Kerry and Waterford will come into effect at 2pm tomorrow afternoon.
Met Eireann said heavy downpours are expected with spot flooding likely along coastal areas.
It will remain valid until 5am on Sunday morning.
Status Yellow-Rainfall warning for Donegal.
Status Yellow-Rainfall warning for Wexford, Cork, Kerry and Waterford.— Met Éireann (@MetEireann) September 27, 2019