"The key message once again to our community is that it is a rapidly evolving situation," Flood Recovery Minister Steph Cooke told reporters Wednesday evening.
Northern Rivers communities had "really borne the brunt of the weather system" over the past month, she said.
The Bureau of Meteorology forecasts another wet night is on the way.
It warned Wilsons River will peak at 12 metres at Lismore, the devastated epicentre of the relentless floods, on Wednesday night after its levees were breached earlier in the afternoon.
Major flooding is expected on numerous rivers including Wilsons, Richmond, Bellinger and Clarence.
Deputy SES Commissioner Daniel Austin said the service has performed more than 55 rescues in the past 24 hours.
A search continues in south Lismore for 55-year-old aged-care nurse Anita Brakel, from Nowra.
She was trapped in her white Holden station wagon in floodwaters from about 10pm on Tuesday.
Ms Cooke told reporters the rapidly worsening weather conditions would impact 28,000 people.
Renewed flooding hit Lismore, Ballina, Byron, Coraki, Bungawalbin and Woodburn on Wednesday.
Byron Bay residents were surprised by a torrential downpour which blanketed the town.
"All the streets look weird. There's just palms and debris and rubbish bins thrown over and huge pools of water in people's yards," real estate agent Travis Lipshus told AAP.
His partner's clothing store was "completely destroyed" with muddy waters submerging valuable stock.
He called on the federal government to provide more assistance.
"How do communities recover from this if it keeps on happening? This is the second time in a month," Mr Lipshus said.
Lawyer Mark Swivel blamed the bureau and the SES for underestimating the severity of the downpour.
"We woke up to a town centre ... that was inundated. There were parts of the town that had never been flooded before," he told AAP.
"In a nutshell the warning systems which failed us a month ago, they failed again."
Labor's spokesman for Emergency Services Jihad Dib said emergency services personnel were doing their best but the government needed to step up.
"The mixed messaging about the river level falling while ... it was rising, only highlights the lack of co-ordination and single point of leadership required in an emergency," Mr Dib said.
He said it was not good enough that Byron and Lismore residents were still dealing with faulty water gauges and broken warning sirens a month after initial flooding.
In Lismore, flood fatigue has set in as the onslaught continues.
"Everyone's exhausted. Evacuation orders started at 4pm yesterday and then got cancelled before the phones started ringing again," Lismore Mayor Steve Krieg told AAP on Wednesday.
"(People are) running on no sleep at the moment. It's hard to put into words. You're feeling angry as well because the messaging hasn't been what it should have been.
"Now you've got to virtually start all of that process from the start again."
Other areas in the state including Coffs Harbour have not been spared recording around 400mm of rain in the past 24 hours.
A severe weather warning is also in place from Grafton to the Hunter region as towns continue to soak for the coming days. Heavy rain is also forecast for the Greater Sydney area.
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