Severe weather continues battering NSW, with the Hunter region and Mid-North Coast next in line for a drenching as western Sydney endures widespread flooding.
About 50,000 people have been ordered or warned to evacuate, and major flood alerts are in place as rivers rise.
Federal Emergency Management Minister Murray Watt said the floods are yet to cross the threshold for a national disaster declaration, but promised support will come from the Commonwealth.
The weather system that drenched Sydney was expected to impact the Hunter region on Tuesday and the Mid-North Coast on Wednesday.
Rivers are rising in the Hunter, and major flooding is occurring at Bulga and Wollombi on the Wollombi Brook, with rain forecast to continue all week.
State Emergency Service Commissioner Carlene York said resources have been directed north, with backup requested from other states.
Another 100 Australian Defence Force members should arrive on Wednesday, with 50 more available to support the eventual clean-up effort, Prime Minister Anthony Albanese said on Tuesday.
He plans to tour flood-hit areas with Premier Dominic Perrottet on Wednesday and has offered whatever support is required from the Commonwealth.
Earlier, Mr Perrottet pleaded with people to follow evacuation orders, saying two of the 22 flood rescues conducted overnight were in areas people had been told to leave.
"They're also putting our volunteers at risk ... if those orders are in place, and your home is affected, please leave," he said.
Crews responded to another call from someone claiming to need rescuing from a roof.
"Very disappointingly ... it turned out to be a hoax," Ms York said, saying the call took resources away from people who genuinely needed help.
Major flooding continues along the Hawkesbury River at Windsor, Sackville, North Richmond and Wisemans Ferry to the northwest of Sydney.
Police were forced to relocate from Windsor to Riverstone station on Tuesday morning following evacuation orders.
Flood Recovery Minister Steph Cooke said about 400 people are in the state's nine evacuation centres, and 150 in emergency accommodation.
About 19,000 homes are without power after rising waters and damaging winds prompted energy companies to cut electricity.
Meanwhile, joint disaster funding has been announced for 23 local government areas.
Ms Cooke said it was an important step to getting support to communities and encouraged people to contact ServiceNSW to access relief.
Senator Watt said the Commonwealth and NSW governments were working to ensure affected areas get assistance quickly.
He said the legislated threshold for a national disaster declaration requires damage to reach a nationally significant level or affect Commonwealth interests.
"While this is a severe disaster, it hasn't reached that level ... we will still provide all of the usual support that would come after a significant disaster like this," Senator Watt said.
The Insurance Council of Australia has declared flooding in NSW a "significant event" which could become a catastrophe if claims increase.
Given repeated flooding, people with ongoing claims will be prioritised.
"Insurers are well prepared to respond to these events, but it is clear the community needs to be better protected from worsening extreme weather and that requires greater investment in mitigation and resilience," ICA CEO Andrew Hall said on Tuesday.
Mr Albanese said some mitigation work is controversial and different views need to be considered.
"What is clear is that we need to get through the immediate crisis ... and then we need to examine any policy response that is required," he said.
NSW Regional Transport Minister Sam Farraway said a major landslip alongside railways in the Blue Mountains could take weeks to repair.
The landslip occurred near Blackheath and has closed the line between Katoomba and Mt Victoria.
"Passenger services and freight cannot travel over the Blue Mountains," Mr Farraway said.
Geotechnical engineers are assessing the landslip, which has grown to about 40 metres long, 20 metres wide and 60 metres deep.
"Transport for NSW is working closely with the freight industry to communicate the impacts and find viable alternatives to move goods and supplies," Mr Farraway said.
