Met Eireann has issued a Status Yellow rainfall warning for Waterford, the only county in the country to be named by the forecaster.
The warning comes into effect on Sunday morning.
"Persistent, and at times, heavy rain during Sunday will lead to accumulations between 25 to 40mm," Met Eireann said.
There is potential for this warning to be extended to include other counties.
The warning is valid from 5am until 9pm on Sunday.