The Bureau of Meteorology warns areas stretching from the Hunter to the Central Tablelands and down the South Coast are in for more rain on Sunday, with thunderstorms and intense rainfall a possibility.
Western Sydney is also in line for heavy rain, with moderate to major flooding possibly returning in the Hawkesbury-Nepean valley.
Some areas could receive up to 140mm of rain in six hours and dangerous flash flooding could follow.
Six deaths have been confirmed in NSW, four of them in Lismore, from flooding that began over a week ago.
State and federal leaders have promised more help and financial aid as some affected areas begin the long clean-up, while others remain underwater.
NSW Flood Recovery Minister Steph Cooke and Deputy Premier Paul Toole visited areas hit by the floods on Sunday morning.
In Coraki, on the Richmond and Wilson Rivers south of Lismore in the Northern Rivers, the local police station was one of many buildings inundated as the town was flooded and cut off from surrounding areas.
As waters recede, the damage is now being assessed.
NSW Police Coraki Sergeant Dean Childs says the town had little chance to prepare for the floods.
"It happened that quick and no one expected it to be that high," Sgt Childs said.
With only a small number of emergency service personnel in Coraki, community members had to step in too.
"To have a flood this size and have the SES in such a small town, it's a smaller SES so we only have a certain number of boats, so we've got all these local people jumping in their own vessels to try and rescue people as well," Sgt Childs said.
NSW Premier Dominic Perrottet on Saturday pledged his government would not "spare a dollar" in funding the recovery.
"After everything we've gone through as a state over the last few years I know we will get through this, as challenging as it seems," the premier said.
Insurance claims had hit about $1.25 billion by the end of Friday, with the lion's share - $1 billion - being submitted from Queensland, industry body the Insurance Council of Australia said.
Meanwhile, the federal government extended the number of local government areas able to access one-off disaster relief cash payments of up to $1000 for adults.
"We continue to closely monitor the flood emergency and our hearts go out to those people whose lives are being devastated," federal Emergency Minister Bridget McKenzie said.