Met Éireann has issued a Status Yellow rainfall warning for eight counties, with localised flooding and hazardous driving conditions expected.
The alert was issued this morning (Wednesday, September 2) at 9:00am; it came into effect at 10:00am and will remain in place until 9:00pm tonight.
The warning affects counties: Galway; Mayo; Roscommon; Sligo; Leitrim; Donegal; Cavan; and Monaghan.
Meanwhile, the UK Met Office has issued a Yellow rain warning for counties Armagh and Down in Northern Ireland.
For the Republic of Ireland in general, Met Éireann says that it will be dull this morning with spells of rain, giving heavy falls in places and a risk of localised flooding.
It will become drier over much of Leinster and Munster this afternoon. Rain will continue in Connacht and Ulster and will spread southeastwards this evening.
Early tonight, rain will continue to affect Munster, Leinster and east Ulster.
It will gradually clear southeastwards with clear spells and scattered showers following from the northwest.
Lowest temperatures of 12° to 15° are given, with moderate southwest winds.