NSW residents are being warned to brace for more deaths from the escalating flood crisis in the state's north as 17 councils are declared disaster zones.
"The situation is distressing for many and will affect more. The ultimate focus now is saving lives and getting people to safety," Premier Dominic Perrottet said on Tuesday.
Hundreds of people are still unaccounted for and at least one man is feared dead after going missing in floodwaters.
Emergency Services Minister Steph Cooke said people should expect more fatalities.
"I think that it is unrealistic that a disaster of this magnitude will mean that there are no lives lost," she told reporters.
Mr Perrottet said the cleanup "and getting communities back on their feet will take weeks, months and years".
"There's still difficult times to go."
Towns across northern NSW, including Lismore and Ballina are underwater and rivers are peaking even as the rain stopped.
The unprecedented floods are much worse than anticipated, with 35,000 people ordered to evacuate their homes and another 310,000 warned to be ready to flee.
Mr Perrottet green lit disaster aid - a mix of state and federal support - after speaking with local mayors in impacted regions with authorities to focus on temporary accommodation.
He also met with Insurance Council of Australia head Andrew Hall with 15,000 flood-related claims made so far.
The Bureau of Meteorology said the weather system which had fuelled the floods was now heading south.
A severe weather warning was issued for coastal areas from the Central Coast to the South Coast, including Sydney.
Wind gusts of up to 125 km/h wind gusts are predicted and the possibility of up to 200mm of rain over six hours from Tuesday night.
The State Emergency Service put out a flood watch for the whole Sydney region, with the worst predicted for areas around the Upper Nepean River.
"People in Sydney and across the South Coast have time. The time to prepare is now," Ms Cooke said.
Things in northern NSW were not going to get better "for a little while", she said.
SES Commissioner Carlene York said the organisation's operational temp was "extremely high", prioritising rescues over property damage.
A NSW budget estimates hearing on Tuesday heard five NSW National Parks and Wildlife Service helicopters remain grounded despite the need in flood-affected areas.
But Ms York told reporters shortly after the NPWS pilots were not trained to perform the highly-skilled technical rescues that SES pilots did and could put more people at risk.
People in South Ballina were told it was too late to leave on Tuesday morning as floodwaters hit the northern coastal town.
People in other parts of Ballina have been ordered to evacuate as unprecedented flooding continues to devastate vast swathes of the state's north coast.
The SES performed 932 flood rescues across the Northern Rivers region in the 24 hours to Tuesday morning.
There were five helicopters helping perform rescues in the Ballina region, along with 46 water rescue personnel and 500 volunteers.
The crisis has engulfed the northeastern part of the state, with multiple major flood warnings including the Tweed, Richmond, Wilsons, Brunswick, Bellinger and Clarence rivers.
Thousands of people spent the night in evacuation centres.
Lismore remains submerged after the Wilsons River peaked at 14.4 metres at 3pm on Monday before starting to fall.
Rescuers in a flotilla of dinghies and inflatables plucked stranded Lismore residents from rooftops and balconies of submerged homes.
Disaster assistance is now available in 17 local government areas.
The LGAs are Armidale, Ballina, Bellingen, Byron, Clarence Valley, Coffs Harbour, Glen Innes Severn, Hornsby, Kempsey, Kyogle, Lismore, Nambucca, Port Macquarie/Hastings, Richmond, Tenterfield, The Hills and Tweed.
