The storm, which has lashed Sydney and other parts of New South Wales since Monday, has dumped more than 30cm of rain in some areas, causing flash flooding.
It is thought that the flooding may have led to the deaths of three people, as well as washing away a number of houses, officials said on Tuesday
The New South Wales State Emergency Service (SES) said it had received more than 3,000 calls for help and had to carry out 19 flood rescues.
As well as torrential rain, damaging gusts of wind of up to 85mph have battered the region, ripping off roofs and blowing over trees.
The ferocious winds also tore down power lines, leaving more than 200,000 homes without electricity at one point.
Transport authorities have advised residents in Sydney to avoid all non-necessary travel until the bad weather eases.
Sydney is reported to have had a month’s worth of rain in just 24 hours, according to data from the Australia Bureau of Meteorology.
Waves of around 11 metres were recorded off the Sydney coast, as giant seas closed many beaches, including the world-famous Bondi beach.
Sydney harbour was also closed, forcing a cruise ship with some 2,500 passengers to wait off the coast, battered by big swells.
Ships attempting to enter the harbour had to be escorted by a harbour pilot, but the wild weather prevented them from boarding the cruise ship to steer it into port.