Met Éireann has warned of possible flooding, public transport disruption and delays as intense rain moves eastwards across the country.
A Status Orange rain warning will come into effect for Cork, Kerry and Waterford at 10pm tomorrow night and remain in place until 5am on Friday.
A separate Status Orange warning has been issued for Dublin, Wexford and Wicklow, where the alert will run from 2am until 8am on Friday.
A Status Yellow wind and rain warning will also apply nationwide, covering all counties from 7pm tomorrow until 10am on Friday.
The national forecaster said heavy rain would spread eastwards, while easterly winds are expected to turn northwesterly and strengthen further, particularly across the south and southeast.
Storm Austen was named by the UK Met Office, with the UK expected to experience the most significant impacts from the storm in terms of wind strength.
Met Éireann has also issued a Status Orange Marine Storm warning for waters stretching from Wicklow Head to Dungarvan to Valentia, and on the Irish Sea south of Anglesey.
North to northwesterly winds are forecast to reach storm force 10 at times. The marine warning will be in effect from 9pm tomorrow night until 7am on Friday.
People are being advised to remain aware of changing weather conditions, with heavy rainfall and strong winds expected to create hazardous conditions in affected areas.
