Thousands of NSW residents are under flood watch as the Bureau of Meteorology issues major warnings across the state.
Emergency personnel performed 11 rescues from floodwaters overnight on Saturday, with more wild weather forecast for the weekend.
Authorities have also issued warnings for communities in northern Victoria along the Murray River.
It comes as the Insurance Council of Australia tells people to prepare their properties for a third year of flood-inducing La Nina weather.
The weather bureau on Saturday issued minor to major flood warnings across NSW including for parts of the Upper Murray and the Peel, Macquarie and Lachlan rivers.
Communities including Tamworth, Gunnedah and Wee Waa are also on alert.
State Emergency Services commissioner Carlene York said the ground was already saturated from record wet weather in NSW in the past two years.
"The dams are at capacity, the ground is saturated, so the water that comes from the sky just has nowhere to go," she told the ABC on Saturday.
Two adults and a child were rescued from the roof of their car in floodwaters near the NSW Central West town of Wellington overnight on Friday.
Spills from the Hume Dam combined with flood waters from the Kiewa River have also caused renewed and prolonged flooding along the Victorian border.
Rises are occurring along the Murray River at Torrumbarry Weir, where minor flooding is possible from Sunday, according to Vic Emergency.
An extended peak is occurring at Barham along with moderate flooding and minor flooding possible at Moulamein in NSW over the weekend.
Along the Edward River, minor floodwaters are slowly easing at Deniliquin. River levels at Stevens Weir peaked on Tuesday, where moderate flooding continues.
The insurance council is urgeing homeowners to review policies, stocktake inventory and prepare their property for heavy downpours.
"The last couple of years have shown the impact that heavy rains can have on property, livelihoods and our own well-being," chief executive Andrew Hall said.
Meanwhile, a $100 million grant program opened on Friday for critical primary producers affected by the February-March NSW floods.
Peak medical organisations have also called for financial aid for health service providers in flood-ravaged communities to help restore services to pre-flood capacity.
