Update 5.40pm: Flood waters in the River Shannon have now reached peak 2009 levels, Offaly Council Council has confirmed.
In its latest update, the local authority stated that the river hit highs which were last seen seven years ago over the past two days, as levels increased by 20mm in Banagher and by 10mm in Shannonbridge.
Council officials say electricity has been cut off to part of Shannon harbour, while it remains off in parts of Portavola Estate in Banagher.
Most householders in the area have voluntarily evacuated because of the lack of power supply and flooding of their boiler houses, but water has not actually entered any of the houses.
Earlier: There is a warning that flash flooding on many roads in the north-east of the country can be expected tomorrow night.
Substantial rain is expected to fall in Cavan, Monaghan, Louth and Meath when a weather system moves in.
Met Eireann forecaster, Gerald Fleming, said: "It'll be during the second half of the day, it's a normal winter weather system, it'll probably bring something like 10-15mm of rain.
"As it clears across the country, it'll clear away through tomorrow night and should be gone by Thursday morning."
The ESB has increased slightly the rate of flow from the Poulaphouca reservoir from 40 to 45 cubic metres a second.
Communications Manager with the ESB, Bernadine Maloney says Kildare County Council believes the River Liffey can handle the increased flow.
She said: "The reservoir at Poulaphouca is quite full and we've been in contact with the Kildare County Council and they advised us that they were able to take more of an outflow from Poulaphouca.
"It is important to get the levels down in Poulaphouca before more rain comes in."