Emergency authorities carried out 13 rescues and received 297 calls for assistance from residents in Sydney, over the past 24 hours, according to local broadcaster SBS News, Anadolu Agency reported.
New South Wales State Emergency Service (SES) said in a statement that at least 10 emergency evacuation orders were in place for the suburbs in the city's northwest.
Riverside communities were warned of flood risks after a dam that provides 80% of Sydney's drinking water started overflowing following the downpour.
While the overflow from Warragamba Dam, southwest of Sydney, has slowed and the rain has eased, flood risks remain. Riverside communities were warned to evacuate or prepare to be isolated due to floodwaters.
"That does not mean that the risk is not there because what we are going to see now is riverine flooding in many areas," acting SES commissioner Debbie Platz told reporters.
SBS News reported that the overflow was moving through the Hawkesbury-Nepean system, swelling rivers despite the heavy rainfall easing.
"If people are not evacuating, then we're asking them to please be prepared for many days of isolation," Platz said.
This marks the third consecutive month the dam has overflowed. The Hawkesbury River was rising toward major flood levels at North Richmond on Saturday morning, but appeared to peak below that level shortly after 8 a.m. local time (2200GMT).
Weather forecasters warned that major flooding could occur in northwestern Sydney, a city of about 5 million, later on Saturday.