Motorists are advised to drive with care following a warning by Met Éireann of heavy rainfall and strong winds in many parts of Leinster and Munster.
Up to 5cm of rain is forecast in some places.
Cork City Council and the Chamber of Commerce are advising home and business owners in the city to take the appropriate precautions.
AA Roadwatch has already reported flooding in parts of Cork city centre, particularly in the Sharman Crawford Street area.
Earlier flooding along the quays has receded.
Met Éireann says it will be windy, especially in coastal areas, and there is a danger of some flooding.
Flooding is likely in places from the rain, but coastal areas have the added threat of flooding due to low pressure, high seas, high tides and onshore gales at times.
In Dublin, high tides combined with low atmospheric pressure and high winds over the next few days will give rise to high sea levels and possibly large waves.
As a precautionary measure the flood gates on the River Dodder are being deployed.
Dublin City Council will deploy sandbags, if required.