A Status Yellow rainfall warning has been issued for the entire country.
Met Éireann says persistent and occasionally heavy bands of rain will cross the country beginning tonight through to Tuesday evening.
While some areas will remain below warning levels, there is a risk of localised spot flooding with a heightened risk of flash flooding in mountainous regions where accumulations are expected to be highest.
The warning is valid from midnight tonight until 7pm on Tuesday.
Met Éireann's weather advisory for Ireland also says unusually high tides combined with strong winds gives an elevated risk of coastal flooding.
Cork City Council says there is a risk of flooding in some low lying areas of the city centre tomorrow night and early Tuesday morning.
Areas most at risk include Sharman Crawford Street, Wandesford Quay, Frenches' Quay, Proby's Quay, Crosses Green, Lavitt's Quay, Kyrl's Quay, Union Quay, Trinity Bridge, Fr. Mathew Quay and Morrison's Quay.
The South Terrace, Ruthland Street, Sawmill Street and the South Mall are also vulnerable.
High tides of note are 8.13pm tomorrow evening, and 8.35am on Tuesday morning.
The UK Met Office has also issued a Yellow rain warning for counties Armagh, Down, Fermanagh, Tyrone and Derry.
Its warning, valid from 5am tomorrow until 3am on Tuesday, says heavy rain may cause some travel disruption and flooding.