Status Yellow wind and rain warnings have been issued for Wednesday ahead of the arrival of Storm Agnes.
It has been named by the UK Met Office and is the first named storm of the season.
Agnes is a deep Atlantic depression, Met Éireann said, that will track close to or over Ireland.
But exact details of the forecast are still uncertain.
The wind warning applies to Leinster and Munster where forecasters say that southerly winds will be very strong and gusty, veering westerly later.
Difficult travel conditions, power outages, fallen trees and coastal flooding are possible.
The rain alert is for eight counties - Carlow, Dublin, Kilkenny, Wexford, Wicklow, Cork, Kerry and Waterford.
Heavy rain, Met Éireann said, could cause difficult travel conditions, localised flooding and poor visibility.
Both warnings will be in effect from 7am to midnight.
The forecaster added that they are set to be updated later today or tomorrow.
A Status Yellow wind warning has also been issued for Northern Ireland.
It will be in place from 12pm on Wednesday until 7am on Thursday morning.
#StormAgnes has been named by the UK Met office for Wednesday. It is the first named storm of the season.— Met Éireann (@MetEireann) September 25, 2023
At the moment we have yellow wind & rain warnings in place.🍃🌧️
Please keep an eye on ➡️https://t.co/juduxcKda8⚠️ for any updates pic.twitter.com/bx5QovEm2W
'Small threat to life' - UK Met Office
Storm Agnes will bring strong winds and heavy rain to the UK on Wednesday and Thursday.
"There is a small chance of injuries and danger to life from flying debris," according to the Met Office in London.
Chief Meteorologist Steve Ramsdale said: "While the precise track and depth of Storm Agnes is still being determined, there's a high likelihood of wind gusts around 50-60mph (80-97km/h) for some inland areas.
"Exposed coastal areas could see gusts of 65-75mph (105-121km/h) with a small chance of a few places seeing around 80mph (129km/h).
"As well as some very strong winds for many, Storm Agnes will also bring some heavy rain, with the highest totals more likely in Scotland, northern England, Wales and Northern Ireland.
"Around 60mm of rain is possible in a few places over high ground in Scotland."
The Met Office said the wind warning highlights the chance of some damage to buildings from strong winds, as well as the possibility of power cuts, with transport disruption also likely.