The heavy rain fell on land already partly soggy, causing the waters to rise rapidly.
Overflowing rivers following four days of heavy rains submerged homes and roads, forcing dozens of people on Tuesday thousands of Sydneysiders to leave their homes.
The New South Wales emergency services, which assisted 22 people overnight Monday to Tuesday, called on some 50,000 people to evacuate.
The floods, heavy rainfall and high winds caused power cuts to some 19,000 homes.
Rain has eased in parts of Sydney, but Flood warnings are likely to persist for several days.
Australia is particularly affected by climate change, regularly hit by droughts, devastating wildfires, not to mention repeated and increasingly intense floods.
Sydney isn't out of danger, now is not the time to slack off, said Carlene York, the state's emergency services manager.
New South Wales Premier Dominic Perrottet has called on people to comply with evacuation orders, saying this event is far from over.
The Federal Government has declared a state of natural disaster in 23 flooded areas of New South Wales, releasing aid for affected residents.
Many residents affected by this new weather episode had already been victims of successive floods that hit the east coast of the country.
These heavy rains fell on an already partly soggy ground which caused a rapid rise in water levels, especially in the western suburbs of Sydney.
Many residents affected by this new meteorological episode had already been victims of the successive floods of the east coast which, in 2021 and in March, caused more than twenty deaths.
It's so sudden, you can't even get out that fast, you can't even move anything, Jenny Lee, a resident of Shanes Park in the western suburbs of London, told AFP. Sydney.
In the western suburbs of Windsor, Tyler Cassel hastily left his house in a canoe.
L& #x27;water rose very quickly, faster than usual, he told Australian broadcaster ABC.
Four days of torrential rains forced thousands of residents from their homes.
It was one of the most terrifying floods I've ever experienced .
Most of the affected areas are downstream of the Warragamba Dam, west of Sydney, which overflowed. It provides most of the city's drinking water.
Rain has eased in parts of Sydney, but flood warnings are likely to persist for several days, warned Jane Golding of the state weather services.