A flooding recovery operation is under way in Newry and Newcastle while an emergency response continues in Downpatrick, a Co Down council has said.
Downpatrick, Newcastle and Newry were the areas in Northern Ireland worst hit by several days of heavy rainfall.
Some rivers in Northern Ireland were described as having reached record high levels as roads flooded.
Police, firefighters, the ambulance service, councils and state agencies have been working with the Red Cross to support areas affected.
A £1,000 payment has been made available to homeowners dealing with flooding through the scheme of emergency financial assistance (SEFA).
People are being advised to only start the clear-up of their property after the water has subsided and to wear protective clothing while doing so.
Newry, Mourne and Down District Council has advised that an electrician should check electrical appliances and a Gas Safe-registered engineer should check gas supplies.
Council chair Valerie Harte said the flooding had been “devastating” for some residents and businesses.
She said council staff had assisted with the distribution of sandbags for the use in constructing flood defences, as well as providing emergency assistance.
“The council has also adapted its services wherever possible to meet the challenging circumstances,” she said.
“Newry, Mourne and Down District Council is now providing practical assistance in the clean-up operation and is ready to play a significant role in the recovery phase.
“Recovery advice for businesses and residents will continue to be posted on our social media channels and can be found online.”
Staff in Newry City Centre Council are receiving support from colleagues at the Lisburn & Castlereagh City Council with the clean-up, and a flooding recovery operation is also under way in Newcastle residential areas as flood water recedes.
In Co Armagh, the train line between Portadown and Dundalk remained closed on Thursday night due to flooding, with bus substitutions in place.
Annagh United Football Club in Co Armagh also saw their grounds damaged by flooding.
The Department for Infrastructure said it expected not be able to work to reduce the floodwater in Downpatrick until Friday when river levels have dropped.
The department said: “Our engineering team has assessed the situation and estimated that it could be tomorrow before we, along with multi-agency partners, can progress the reduction of the floodwater at Market Street, Downpatrick.
“The main reason for this is that the water levels in the river and its smaller tributaries need to decrease before we can make meaningful progress.”
A spokesperson for the department said rivers in some areas had reached record levels and remained very high on Thursday morning.
They added that it will take some time for water to drain away.
“Lough Neagh will continue to rise but at this stage is expected to peak tomorrow at a level below what was experienced in the winter of 2015,” the spokesperson said.
“We have already engaged with colleagues in local government and councils about the recovery stage, and we will play our part in that in whatever way possible.”
The department, along with Newry Mourne and Down Council, met with local businesses and elected representatives in Downpatrick on Thursday to advise them on the problems associated with removing floodwater from Market Street.
It said it has been working on a plan for pumping water out over long distances using high-volume pumps, which will begin once river water levels are low enough.
“We couldn’t do this today because it would have resulted in water flowing back to Market Street due to high river levels at present,” it said.
“Whilst there have been some indications of floodwaters increasing slightly in Downpatrick, water levels in the Quoile River have peaked and have begun to fall from early morning.
“The precise timing of the operation cannot be provided due to the unique nature of the task and the dependence on falling river levels.
“We appreciate everyone’s patience as we work to manage the situation,” it said.
