Heavy rain is expected in the northern half of the country with Met Éireann issuing a status yellow warning.
The rainfall warning is in place for all of Connacht, Cavan, Monaghan, Donegal, Longford, Louth, Westmeath and Meath.
The warning came into effect at 6pm and will remain in place until 6am tomorrow.
Met Éireann has warned of “heavy rain” and of a “risk of localised flooding”.
A status yellow rain warning has also been issued for all of Northern Ireland by the UK Met Office.
That warning is in place until 9am on Thursday.
The UK Met Office said that “heavy rain” will bring “some flooding and transport disruption”.
Meanwhile, Thursday will see some bright or sunny spells before rain sets in.
Rain “will develop in the southwest during the afternoon and spread northeastwards through the evening,” according to Met Éireann.
Friday will be “generally cloudy with scattered outbreaks of rain” while the forecaster is predicting that the outbreaks "will become more isolated during the afternoon, allowing some sunny spells to develop”.
In the southwest, rain will set in by afternoon and will become “more persistent and occasionally heavy through the evening”.
Saturday is expected to see rain in the morning which will clear to leave “a dry afternoon with sunny spells”.
Saturday night will see temperatures drop below zero - ranging between minus one and five degrees.
Met Éireann has said that Sunday “is currently expected to be a wet and windy day.
“A cold day too, especially in the north and east, with falls of sleet or snow possible”.