Met Éireann has issued a Status Yellow rain alert for the entire country.
The warning comes into effect at 3am tomorrow and will remain in place until 3am on Monday.
The forecaster warns that "heavy rain with isolated thunderstorms may cause disruption and localised flooding".
It will also be humid and breezy tomorrow with temperatures of between 17C and 20C.
Meanwhile, a Status Orange rain warning has been issued for Cork and Waterford, valid for the same hours as the nationwide yellow warning.
Met Éireann stated: "Persistent heavy rainfall with isolated thunderstorms will cause disruption and localised flooding."
A Status Orange rain warning has also been issued for Kerry, again starting at 3am tomorrow until 3pm in the afternoon.