Families had to be rescued from their homes as the Republic was hit with gale force winds, heavy rain and serious flooding in several parts.
Limerick was among the areas worst hit. Emergency services worked flat out in a number of housing estates where people were left trapped in their homes.
Half a dozen boats were used to rescue several elderly people from the city's Lee housing estate. Fire crews were also involved in a major operation. Ambulances were on standby.
Some residents managed to wade through the water.
In the neighbouring Lahinch area giant waves washed over three storey guest houses on the seafront and huge boulders were swept away into a car park.
With winds gusting at up to 120km/h, (75 mph) Met Eireann issued a status orange weather warning for Munster, Leinster, Connacht and parts of Ulster. At one stage more than 5,500 properties were without power, 4000 of them in Ennis, Co Clare.
Houses near Castlegregory, Co Kerry were cut off when rocks, boulders and other debris blocked the only access road to the Kilshannig area.
Parts of Galway city and Tralee, Co Kerry were also flooded and emergency crews helped provide sandbags and in Cork city, a stretch of the River Lee overflowed its banks.
AA Roadwatch warned drivers to be careful because of the worsening weather and several flights from Dublin Airport to Britain, Paris and Madrid had to be cancelled.
Meanwhile in Northern Ireland, police warned drivers to avoid parts of Newry and Warrenpoint, Co Down because of floods on some roads.