Hundreds of homes and businesses were severely flooded after parts of Co Cork got more than a month's rainfall in less than 24 hours during Storm Babet.
The town of Midleton was one of the worst affected as premises were swamped with floodwaters and its main street was impassable for a time.
Motorists were urged to avoid the town if possible and use an alternative route.
Cork County Council said that more than 100 properties were flooded in Midleton, and a rest centre was established at the town's community centre to help people who had to evacuate properties.
According to Fianna Fáil TD for Cork East James O'Connor, a local hospital in the area had to be evacuated.
Mr O'Connor spoke to RTÉ's Drivetime from Midleton's Main Street and described "a scene of great devastation and sadness" with dozens of emergency services vehicles, volunteers, the RNLI, coast guard, reserves and gardaí all trying to help people with their homes.
He said that businesses have been very badly damaged and that homes and gardens were "underwater" .
Mr O'Connor added that he had not seen or heard of any flooding of this scale before.
He said that he has made contact with Minister of State Patrick O'Donovan who will make a visit.
He has also spoken to Tánaiste Micheál Martin and will be speaking to the Taoiseach.
Cork County Council said that a Coordination Centre has been established at Midleton's fire station to coordinate arrangements.
A "month's worth of rain" had fallen in the town in the last 24 hours, according to Cork County Mayor Cllr Frank O'Flynn.
"I am especially conscious of the advanced preparations that were undertaken by Cork County Council in mitigating the effects of this event and how, despite every effort, homes, businesses and road users have been impacted," he said in a statement.
Mill Road and Main Street in Midleton were underwater and the flooding entered and damaged dozens of homes and businesses there. Many properties were evacuated.
Cork County Council staff also dealt with flooding at several towns and villages in the north and east of the county.
The council said that properties in Whitegate, Rathcormac, Glandore, Ringaskiddy, Carrigaline, Raffeen, Halfway and Casteltownbere were also been flooded.
Killeagh in east Cork was also been badly affected, with a number of properties flooded there also. There was also been some reported flooding in Youghal.

In the city, Blackpool was closed off, with a number of properties flooded there.
Homes were also evacuated by Cork City Council and Cork City Fire Service staff at Commons Road, Great William O'Brien Street and Dublin Street.
A convenience store and a pharmacy in Blackpool was also flooded.
Several roads in Ballyvolane, Blarney, Carrigrohane, and Tower were reported as impassible.
Glanmire was also been badly affected, with traffic unable to get through the area.
On the southside of the city cars have been abandoned and flooded on Monaghan road and Centre Park road.
In a statement, the Defence Forces said that personnel were deployed to Midleton following requests from the local authority.
It said that Transport and Engineer assets can assist with transporting people from affected areas.
Fianna Fáil TD O'Connor said financial help is going to be needed and due to previous localised flooding, flood insurance was not offered to many business owners.
He also said that what has happened was the consequence of weather that would have been attributable to a red warning by Met Éireann, but only an orange one came.
"We are going to need the Government to do everything they can to help the local people here in east Cork and the local businesses that have been so badly affected" he said.
A Status Orange rain warning was in effect for three counties until 8pm.
Status Yellow rain warnings for Wexford and Wicklow had been updated to Status Orange and was in effect until 8pm.
Those two counties, as well as Dublin, were placed on a Status Yellow alert until 5am Thursday morning.
Met Éireann said spells of heavy rain and blustery east-to-southeast winds may lead to localised flooding, difficult driving conditions and possible wave overtopping at high tide.
Meanwhile, Iarnród Éireann suspended services between Cork to Cobh and Cork to Middleton due to flooding, with bus transfers in operation.
A separate Status Yellow rain warning was issued for most of Leinster, Cavan, Donegal and Monaghan and was valid until 8pm this evening.
#AfternoonUpdate
— Met Éireann (@MetEireann) October 18, 2023
Heavy rain will affect the country today as bands of rain associated with #StormBabet push northwards over the country ☔️🌧️
Flooding is expected across southern areas with orange warnings out for a number of counties ⚠️
More here 👇https://t.co/Xg3aMJlyuS pic.twitter.com/yMfWaqjJoi
Storm Babet is the second named storm of the season and the UK Met Office said Yellow severe weather warnings for wind and rain will be in place for much of the week.
A Yellow warning has been issued for Antrim, Armagh and Down until midday on Thursday, with the Met Office warning of a prolonged period of heavy rain expected.
Many roads in west Waterford also experienced significant flooding, with flooding reported on the N25 and N72.
Lismore, Tallow, Clashmore, Aglish, Ballyduff Upper and the adjoining hinterlands have been experiencing continuing heavy rainfall.
Humanitarian assistance
Minister for Social Protection Heather Humphreys has said humanitarian assistance is available to support those affected.
She said: "I'm very conscious that Storm Babet is causing severe flooding and disruption, particularly in the Midleton area of Cork.
"Other parts of the county and indeed country may also be affected until the storm passes.
"My department is liaising on the ground with the people affected to make sure they have access to the help that they need.
"The Humanitarian Assistance Scheme is open and support is available."
"If any homeowner affected by Storm Babet needs to access these supports, they can contact the Community Welfare Service by phoning 0818 60 70 80."
RTÉ Brainstorm:
Why have we seen so many storms in recent years?
Additional reporting Paschal Sheehy, Conor Kane