Preparations have been made ahead of expected heavy rainfall on Sunday night.
Met Eireann has issued a status yellow rainfall warning for 19 counties across Ireland from 8pm on Sunday to 8am on Monday.
The forecast heavy rain on Sunday night is expected to lead to “accumulations of between 20 to 25mm” which it is feared could lead to flooding.
The rain is expected to be followed by sleet and snow.
Some of the areas expected to be worst affected are towns along the River Shannon.
Flooding remained in Athlone, Co Westmeath, on Sunday from earlier rain.
Staff from Westmeath County Council were on the ground installing defence measures, including an inflatable aquadam.
Minister of State at the Office of Public Works with responsibility for flooding, Kevin “Boxer” Moran, said the river’s water levels are expected to exceed the 10-year flood mark on Tuesday.
Mr Moran visited Athlone on Sunday where he tweeted a video of efforts to protect a house in Ballykeeran with sandbags and a pump.
He added that local authorities from Cavan to Limerick were on high alert.
Meanwhile, Northern Ireland is set to be affected by a yellow warning for snow and rain on Monday morning, with some travel disruption likely.
The Met Office alert comes into effect at midnight on Sunday until noon on Monday.