Met Éireann has extended a status orange warning for storm force winds tomorrow to the whole country.
Storm Brendan will bring sustained southerly winds of up to 80 kilometres an hour.
However, exposed areas can expect winds of up to 130 kilometres an hour.
The warning comes into effect at 5 am tomorrow for counties in the west and southwest, and 8 am for the rest of the country.
Dublin City Council will be putting up flood defences on the northside tomorrow morning due to Storm Brendan.
It will also be closing the car parks at Clontarf and Sandymount from 6 am.
The local authority may also have to close some flood gates along the River Dodder in the Ballsbridge area.
Alan O'Reilly from Carlow Weather says people living near the coast will need to take extra care.
He said, "Coastal flooding could potentially be the biggest impact from Storm Brendan."
The first effects of the storm are expected to be felt later tonight.