Met Éireann has issued two weather warnings for the whole country.
Status Yellow rainfall and wind warnings have been issued for the entire country as Storm Dennis approaches.
Met Éireann says there will be spells of heavy, thundery rain tomorrow, which will lead to some flooding.
The forecaster also predicts winds of between 50km/hr and 65km/hr with gusts up to around 100km/hr, strongest on exposed coasts and hills.
The rainfall warning comes into force at 3am tomorrow morning and will last until 8pm on Saturday night, while the wind warning begins at around 6am and finishes at around 9pm on Saturday night.
Forecaster Deirdre Lowe said: "The first of the strong winds will land on the west coast towards the end of Friday night, becoming very windy countrywide on Saturday morning with widespread, heavy, thundery rain.
"There is a risk of flooding in parts on Saturday, especially near rivers that are very high at the moment and coastal areas in the very strong and gusty, south to south-westerly winds."
Winds are expected to pick up further on Sunday, especially on the west coast as Storm Dennis lingers over the country.
However, she said Sunday is when Storm Denis will hit hardest, adding: "Sunday we're going to have the worst of the winds."
The AA's Barry Aldworth is urging anyone out on the road to drive carefully and sensibly.
Mr Aldworth said: "The most important tip we always give people is to reduce your speed, allow extra distance between yourself and other vehicles in front of you.
"Only attempt to drive through flashes of water in the road if you feel comfortable that you know the level of the water. If you are unsure, it's better to try and find another way around it. Drop your gears, drive through it slowly."
