A status yellow rainfall warning has been issued for Munster and Leinster.
Forecasters say a spell of heavy rain will move up from the south this afternoon.
Around 25 to 35mm of rain is expected, with the most significant amounts over southern and eastern counties.
The warning comes into effect from 3pm today, and is valid until 6am tomorrow morning.
Showers in the north and northwest today, but elsewhere it will be mainly dry and bright at first. However, rain will spread up over much of Munster and south Leinster this afternoon, turning heavy later in the day. Highest temperatures of 8 to 11 degrees. pic.twitter.com/nawXOiDfcE
— Met Éireann (@MetEireann) March 5, 2019
Meteorologist Harm Luijkx explained: "We are in an unsettled spell of weather, as we've seen in the last few days.
"The rain will start late this afternoon. It will be heavy then in the evening and early tonight, and will clear then again before tomorrow morning."
Met Éireann is forecasting residual patches of light rain and drizzle at first on Wednesday.
However, clearer, brighter intervals with showers are expected throughout the morning and afternoon.