Parts of Limerick city have been flooded as water levels in the lower and mid sections of the River Shannon continue to rise.
A school, a number of homes and an electric sub-station were caught in rising waters when a canal burst its banks in the Corbally area of Limerick.
Elsewhere in the city, cars belonging to a number of rugby fans who attended the Munster vs Leicester Tigers game at Thomond Park on Saturday night were almost entirely submerged in water.
Fire-fighters were using heavily lifting machinery on Sunday in an effort to move some flooded vehicles.
An increase in the flow of water from the Parteen Weir, which controls the Shannon's level through Limerick, has heightened the risk of flooding.
ESB said the flow increase was required to cope with the volume of water accumulating upstream in Lough Derg.
An ESB spokesman said: "This level of water flow is likely to lead to increased flooding of roads, land and property in the vicinity of the Shannon downstream of Parteen Weir including the areas of Springfield, Montpelier, Castleconnell, Mountshannon (Annacotty) and the University of Limerick."
Further up the Shannon, Athlone remained on flooding alert.
Members of the National Coordination Group met again in Dublin to discuss and co-ordinate the response to the floods.
After the meeting, a spokesman said: "Local authorities remain on standby and continue to monitor the situation and in the areas where further flooding may occur - the necessary preparations are supplemented by the Defence Forces and other service providers when and where required."
Water levels have fallen slightly on the upper stretches of the Shannon over the weekend while, in Northern Ireland, Upper Lough Erne in Co Fermanagh remains at a high level.
A number of roads in Co Fermanagh are impassable and in Enniskillen, where Upper and Lower Lough Erne meet, there remain pockets of flooding down at the waterside.
Met Eireann said rain across Munster and south Leinster would slowly move northwards through Sunday bringing some persistent falls to Atlantic coastal fringes.
The forecaster said Monday and the rest of next week would see a move towards "more normal weather".
Met Eireann said: "There will be further rainfall throughout the week but nothing of an exceptional level."
The UK Met Office has issued a yellow rain warning for Fermanagh through most of Sunday, prompting fears of further flooding in the county.
A spokesman for the NI Rivers Agency said: "Water levels in Upper Lough Erne haven't changed much in the last 48 hours and remain 150mm below the 2009 peak."
He said gauge readings indicated the flood peak was " making its way downstream".
He added: "We remain cautious as there is more rain forecast for today (Sunday), however the accumulations are not high so we don't expect to see rising water levels."