Met Eireann has issued a Status Yellow rainfall warning for five counties as up to 50mm of rain will lash the south of the country.
The alert covers counties Kilkenny, Wexford, Waterford, Cork and Tipperary and comes into effect at midnight on Wednesday.
Mey Eireann says the caution will remain in place for 36 hours until 12pm on Thursday.
A Met Eireann forecaster said: "From Wednesday night to noon on Thursday, spells of heavy rain at times will give amounts of 30mm to 50mm with a risk of spot flooding."
The deluge will be accompanied by fresh south or southeast winds and highs of 9C to 11C.
Wednesday night will be milder than previous nights, but it will be windier with some heavy showers forecast.
Wednesday night will be milder than previous nights, but it will be windier with some heavy showers forecast.
Meanwhile, Tuesday will see a band of rain spreading to all areas during the afternoon. Highest temperatures will range from 9C to 11C.
"Cloudy for a time in all areas today with a band of rain spreading east to all areas.
"Eastern areas will begin dry and mainly dry conditions in turn will follow from the west with sunny spells.
"Fresh southeast winds will veer southwest and slacken. Highest temperatures of 9C to 11C."
