Authorities say a renewed flood threat for parts of the already sodden NSW Northern Rivers and Mid North Coast could be potentially "life-threatening" as some residents in the flood-ravaged region are ordered to evacuate.
Evacuation orders have been issued for parts of north and south Lismore, and low-lying parts of Kyogle, as a moderate to major flood warning was issued for the Wilsons River from early Tuesday.
Those living in North Lismore have now been told to leave by 9pm, while in South Lismore and Kyogle it's 10pm.
An evacuation warning is also in place for the Lismore CBD.
Scott McLennan from the State Emergency Service (SES) said his organisation was being assisted by a range of bodies, including the Australian Defence Force and NSW Police, to alert residents.
Mr McLennan said the situation was moving rapidly but he believed crews were well-resourced in the "unlikely event" that rescues would need to be made.
"We have lots of people poised, positioned, ready to assist the people," he said.
There is a flood watch for moderate to major flooding from Tuesday in the nearby Richmond river, and further south in the Orara, Kalang, and Bellinger rivers.
"Our soils and catchments are already saturated, meaning we're going to see quick responses in our rivers, creeks, and streams," said Dean Narramore from the Bureau of Meteorology.
"It will be a period of heavy rainfall with a risk of significant flash flooding and riverine flooding across the north and north-east of NSW."
Acting commissioner of the NSW SES, Daniel Austin, said the "short sharp bursts of rain" could "pose a risk to life and property" in those areas.
Mr Austin said Sydney's Warragamba Dam is expected to spill "as early as this evening but potentially more likely tomorrow, however flood watches for that catchment remain at minor level".
Residents move to higher ground
Adam Perry lost everything in his Lismore home and is grateful to have recently been provided a temporary motorhome at a caravan park.
But today he is on the move again because of the threat of renewed flooding in the town.
Mr Perry thinks it is the right decision to evacuate, even if the town levee does not top.
Dozens of the government-funded motorhomes are now being driven to Alstonville, a 20-minute drive away, on the flood-free plateau.
The father-of-three is still trying to put together the pieces of his fractured life that have been turned upside down.
"It's been four weeks of rain," Mr Perry said.
"What hasn't been destroyed by water has been stolen."
Evacuation centres opened
The Bureau of Meteorology is expecting intense falls of around 100 millimetres in already saturated catchments, but at this stage it is not predicting flood water to breach the Lismore city levee.
Further south, the Coffs Coast region is expected to receive falls of 150-200mm, which could trigger moderate flooding.
A minor to moderate flood watch is also in place for coastal catchments between the Tweed in the state's north and Sydney's Hawkesbury Nepean Valley.
An evacuation centre at Ocean Shores, north of Byron Bay, has reopened in response to the elevated concerns about flash flooding.
The centre had only closed last night after being open for four weeks after the catastrophic flood that hit the region.
Flood recovery coordinator and Assistant NSW Police Commissioner Mal Lanyon said the whole community needed to be prepared for this weather event.
"But it isn't stopping recovery, and certainly not stopping our commitment to move forward to have a more permanent solution."
Assistant Commissioner Lanyon said there are currently 1,200 people in emergency accommodation in Lismore, but he knows the figure of people displaced is much higher.
"We certainly know from the houses that have been impacted that there were significantly more people then that are now living in other arrangements," he said.
