Met Éireann has issued a Status Yellow rain warning for counties Donegal, Galway and Mayo.
The warning is in place for a 24-hour period, from 9:00p.m tonight (Wednesday, September 29) until 9:00p.m tomorrow (Thursday).
The national forecaster has warned that there will be spells of heavy rain at times for those counties, with accumulations of 30mm possible.
There is also a Status Yellow gale warning in place from 9:00p.m tonight until 9:00a.m tomorrow.
Southerly winds are expected to reach gale force eight at times tonight and tomorrow morning on Irish coastal waters, from Valentia to Malin Head to Carnsore Point and on the Irish Sea.
From 11:00p.m tomorrow night until 6:00p.m on Friday there is another Status Yellow gale warning for all coasts of Ireland and on the Irish Sea.
West to northwest winds will reach gale force eight at times.
Met Éireann’s national forecast shows that tonight will be wet and windy, with widespread rain for a time, accompanied by fresh to strong southerly winds.
Drier conditions, with showers, will follow from the Atlantic and winds will veer southwesterly, moderating overland, but remaining strong in coastal areas.
There will be minimum temperatures of 6° to 11°.
Tomorrow will have some bright, dry spells, mainly in the east and south, but it will be mostly cloudy, with scattered showers and more persistent rain at times in the west and northwest.
In the early evening, rain will turn heavy in Atlantic coastal counties, extending eastwards during the evening and early night, with some heavy falls in Connacht and west Ulster.
There will be maximum temperatures of 13° to 16° with moderate to fresh southwesterly winds, strong at times in coastal areas.
It will be a windy night with rain clearing eastwards but followed by blustery showers or longer spells of rain.
There will be lowest temperatures of 6° to 9° in moderate to fresh and gusty southwesterly winds, veering westerly and increasing strong in the north and northwest.
Friday will be a day of sunny spells and showers, heaviest and most frequent over the western half of the country with a risk of isolated thunderstorms.
There will be good dry spells at times in eastern areas. There will be highest temperatures of 11° to 14° generally in fresh and gusty westerly winds.
On Friday night, scattered showers will continue in Atlantic counties overnight, becoming more isolated with good clear spells further east.
Towards morning, showers will merge to longer spells of rain. There will be lowest temperatures of 6° to 9° in mostly moderate southerly winds.