Met Éireann has warned of further flooding following heavy rains. Torrential rain has already forced the closure of Cork University Hospital's accident and emergency and X-ray departments.
The weather forecasters issued a series of flood warnings last night after yesterday's downpours were expected to continue. Met Éireann predicted as much as 60mm could fall before dawn, increasing the risk of flash flooding.
A total of 40 patients were affected by the flooding at Cork's University Hospital, forcing the closure of the two departments.
A number of other areas, including the radiotherapy unit, operating theatres, laboratories and supplies departments, were also affected by the flooding, but a Southern Health Board spokesman said that no out-patient treatments had to be cancelled.
In-patient care was also unaffected by the flooding, but the SHB was last night advising anyone requiring accident and emergency services to go to either their GP, the Mercy Hospital or the South Infirmary/ Victoria Hospital.
Met Éireann's warnings last night focused in particular on the south and south-east counties of Wexford, Waterford, Carlow and Cork.
These were most likely to be the worst affected as thunderstorms and heavy downpours were recorded yesterday afternoon and last night.
The forecasters added the severity of the water levels would depend on how local drainage systems coped with previous falls.
"The lack of wind at present has meant that storms are not moving and are depositing large amounts of rain in concentrated areas," according to Mr Gerald Fleming of Met Éireann.
Mr Fleming said Ireland could easily experience scenes comparable to Boscastle in Cornwall earlier this week. "It is quite possible when you consider the amount of rain involved. Areas like Kilkenny or the Galtees, which has a landscape similar to that of Boscastle, could see some extreme conditions," he added.
Flooding was reported in several areas in Dublin, with over 20mm falling in three hours yesterday.
The DART line between Greystones and Dún Laoghaire was closed for a half an hour yesterday morning because of the heavy rain. Localised flooding was also reported in Baldoyle on Dublin's north side.
In Cork, continuous heavy rains yesterday afternoon led to traffic congestion and delays for motorists in Cork city and county. Gardaí and local authorities reported surface water flooding on several important roads.
According to Met Éireann at Cork Airport, some 20mm of rain fell there between 3 p.m. and 5 p.m. yesterday at the airport's weather station.
Gardaí in Cork city reported heavy flooding on Sarsfield's Road, Wilton Road, Togher Road and Melbourne Road in Bishopstown, while there was also heavy flooding in the Palmbury area of Togher, which was badly hit by flash floods two years ago.
Elsewhere in the city, there was flooding on the Lower Glanmire Road going east out of the city, while Sunday's Well Road and the Lee Road on the western side of the city were also under several inches of water after the heavy downpours yesterday afternoon.
Sgt Peter Murphy of Anglesea Garda station urged people to be careful. "Our advice to motorists is to slow down, light up and show a bit of consideration for other road users, in particular cyclists and pedestrians," he said.
Aer Rianta at Cork Airport reported that an Aer Lingus flight from London had to divert to Shannon at the height of the heavy rains at around 3.30p.m. but it later returned with the passengers to Cork, resulting in a delay in the later return flight.
The rain is expected to ease later this evening, and tomorrow is to be cooler and somewhat breezy, according to Met Éireann. Further heavy rain is expected for Saturday and Sunday.