Met Éireann has named the first storm of the season and issued a Status Yellow wind warning along with a Status Yellow rain warning for 14 counties as the country also braces for the "wet and very windy" arrival of Hurricane Humberto.
Co Kerry will be under a Status Orange rain warning from 6am to 8pm on Thursday, with flooding expected and very difficult travelling conditions also possible.
That warning will be in place from 6am to 8pm on Thursday.
The Status Yellow rain warning applies to Donegal, Longford, Cavan and the provinces of Connacht and Munster and will also be valid from 6am to 8pm on Thursday.
The wind warning, covering the whole country, will come into effect at 12pm on Friday and be valid until midnight on Saturday.
Storm Amy will bring strong to near gale force and gusty southwesterly winds.
7-Day Weather Forecast: September 29th to October 5th
Met Éireann meteorologist Ailís Hankinson told RTÉ's News At One there will be "a lot of rain" on Thursday before the arrival of Storm Amy on Friday.
"So, with that rain tomorrow, we do have a Status Yellow rain warning in effect from 6am to 8pm tomorrow for much of Munster, Connacht, and then counties in Leinster and Ulster as well.
"Then on Friday, we'll see Storm Amy, and at the moment now it's a feature that's being fuelled by tropical remnants in the tropic west Atlantic, and when that warm, moist, tropical air meets the cooler air, after it transitions it then gets picked up by a strengthening jet stream which is sending it across to us, across the Atlantic.
"It is forecast to rapidly intensify, becoming Storm Amy as it reaches us then on Friday."
Ms Hankinson said there is a Status Yellow wind warning for the entire country for Friday, however details remain uncertain and will become clearer over the coming day.
"We can expect some impacts, especially after that rain tomorrow, the ground will already be quite saturated. And with Storm Amy as well, it is more of a wind event but we will see some heavy rain in that as well, so we could see some localised flooding."
She added that there could also be felled trees or blocked drains, with trees still in leaf at this time of year.
The now Category 4 Hurricane Humberto is currently tracking northeastwards from the southeast coast of America towards Ireland at around 130km/h, but is expected to slow significantly before reaching our shores.
However, weather models say it will become re-energised by the jet stream - a fast-flowing current of air above the North Atlantic - which will bring stormy conditions from Friday morning until late evening.
The latest track shows the centre of the storm front missing Ireland as it heads toward Scandinavia - but there are concerns that it will pass close enough to Ireland's north west coast to deliver damaging gale force winds.
The storm will sweep past Ireland's north west coast over Friday bringing potentially powerful winds and torrential rainfall.
Meteorologists are carefully tracking the path of the former hurricane which is now expected to track much closer to Ireland than initially expected.
Clare, Galway, Mayo, Sligo and Donegal will bear the brunt of the strong winds on Friday with parts of the midlands and Ulster also set to be impacted.
Motorists have been warned they could face challenging driving conditions including fallen trees, storm debris and localised flooding.
The UK Met Office has issued Status Yellow wind warning for Antrim, Armagh, Down, Fermanagh, Tyrone and Derry which will be in force from 4pm on Friday until 6am on Saturday.
A small craft marine warning is already in place for Thursday and Friday.
Met Éireann has also issued a Status Yellow gale warning for Fair Head to Carlingford Lough, Carnsore Point and the Irish Sea from 5pm on Thursday until midnight on Friday as winds are expected to reach gale force eight.
A Status Yellow gale warning - for winds up to strong gale force nine - will be in force for all Irish coasts and the Irish Sea from 9am on Friday until 3pm on Saturday.
Met Éireann confirmed "very windy and wet conditions" on Friday, turning cooler this weekend.
Tonight will be cloudy with widespread rain which will carry on into the morning, heaviest in the southwest. It will be a mild night of between 12C to 15C.
Tomorrow will be wet and blustery with the possibility of localised flooding, Met Éireann said. Winds will build along the coasts with highest temperatures of 13C to 17C.
Tomorrow night, rain will clear to the east by night before cloud thickens in the west as Humberto lingers off the west coast. Highest temperatures of 9C to 12C.
Friday will see heavy rain and wind spreading northeast through the morning. Gale force winds will be possible along the west coast. Heavy rain will ease to lighter rain by the evening, with highest temperatures of 15C to 19C. Friday night will still be windy, particularly in western counties, with long spells of rain.
The national forecaster says Saturday and Sunday will be brighter and drier, though cooler, with temperatures of 12C to 16C.