Thousands more residents were ordered to leave their homes on the east coast on Tuesday after rivers swiftly rose past danger levels.

The latest wild storm cell brought a year's worth of rain in three days to some areas of the country.

Torrential rain has caused dams to overflow and waterways to break their banks, bringing a fourth flood emergency in 16 months to parts of the city of five million people.

Footage on social media showed submerged roads and bridges, while emergency crews rescued stranded people from partially submerged vehicles that became stuck in rising waters.

Emergency response teams made 100 rescues overnight of people trapped in cars on flooded roads or in inundated homes in the Sydney area, state emergency service manager Ashley Sullivan said.

New South Wales Premier Dominic Perrottet said evacuation orders and warnings to prepare to abandon homes were given to 50,000 people, up from 32,000 on Monday.

He added that "this event is far from over" and warned drivers to be careful as there are still "substantial risks for flash flooding".

Although the Bureau of Meteorology (BoM) said the storm cell is likely to ease in Sydney from Tuesday, the risk of flooding could remain throughout the week.

Some regions have received 800mm (31.5 inches) of rain since Saturday, eclipsing Australia's annual average rainfall of around 500mm (20 inches).

Experts say the severe rainfall in the country has been worsened by climate change.

The federal government has declared the floods a natural disaster, helping flood-hit residents receive emergency funding support.

Emergency crews also continued rescue operations battling rough seas to tow a bulk carrier ship that lost power off Sydney's coast after tow lines broke in severe weather, officials said.

Officials previously warned that the floods could be worse than the others that have hit the city's suburbs in the last 18 months.

In recent years Australia has seen more extreme weather with droughts, bushfires, and floods becoming more common and intense as global weather patterns change.

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