A status orange weather warning is in effect as forecasters warn that some of Leinster will be hit with rainfall of 40 to 60 millimetres.
Met Eireann has warned that localised flooding will be a risk tomorrow due to heavy rain across Dublin, Louth, Wexford, Wicklow, Meath and Monaghan.
The orange warning will be in effect from tomorrow at 6am until Friday at 9am.
Meanwhile, a status yellow warning will be in effect tomorrow across Munster, Connacht, Carlow, Kildare, Kilkenny, Laois, Longford, Offaly, Westmeath, Cavan and Donegal.
This afternoon, it will be mostly cloudy in Ulster, Connacht and much of Leinster with showers or longer spells of rain.
Much of Munster and south Leinster will see sunny spells today, but scattered showers will move over west Munster.
Highest temperatures will be around 9 to 12 degrees with moderate southerly breezes today.
This evening will be mainly dry but heavy rain will develop in the west shortly after midnight and will spread across Munster, Connacht and south Leinster overnight with a risk of flooding.
It will become windy also as southerly winds increasing strong and gusty with gales in some coastal areas. Lowest temperatures this evening will be from 5 to 7 degrees.