More heavy rains set to drench Sydney as thousands evacuate

Fresh evacuation orders were issued for tens of thousands of Sydney residents on Monday after relentless rains flooded several suburbs in Australia's largest city, with officials warning of more wild weather to come.

An intense low-pressure system off Australia's east coast is forecast to bring more heavy rain through Monday across New South Wales after several places in the state were hit with about a month's rain over the weekend.

With about 30,000 residents in New South Wales state facing evacuation, frustration swelled in several suburbs in Sydney's west after floods submerged homes, farms and bridges there, some for the third time this year.

"It's just devastating. We are in disbelief," Camden Mayor Theresa Fedeli said.

"Most of them have just come out of the last flood, getting their homes back in place, their businesses back in place and unfortunately we are saying it is happening again."

An operation was underway to rescue 21 crew members from a cargo ship, which lost power south of Sydney and risked being swept ashore, local media reported.

"It has been a very difficult time for many months to have this flood event off the back of others, (it) makes it more challenging," New South Wales Premier Dominic Perrottet said during a televised media briefing.

No loss of lives has been reported so far as officials urged people to leave their homes when ordered and avoid driving on flooded roads.

Tracey, a resident from flood-hit Windsor, said she can't cope with the frequent floods.

"We are over it. We are so over it. (This) is a bit much for us," she told ABC television after returning home to rescue some of her animals.

Australia 'under-prepared'

About 100 millimetres (4 inches) of rain could fall in the next 24 hours over a swath of more than 300km (186 miles) along the New South Wales coast from Newcastle to the south of Sydney, the Bureau of Meteorology said.

"We are expecting the rain to pick up again from this afternoon," Jonathan How, BoM meteorologist said.

More than 200mm of rain have fallen over many areas, with some hit by as much as 350mm since Saturday.

Climate change is widely believed to be a contributing factor to the frequent severe weather events, the Climate Council said, adding Australia is "under-prepared".

The wild weather could trigger flash floods and landslides, with river catchments already near full capacity after the La Nina phenomenon, typically associated with increased rainfall, dominated Australia's east coast over the last two years.

Bad weather has delayed by 24 hours Monday's scheduled launch of a NASA rocket from the Arnhem Space Centre in north Australia, operator Equatorial Launch Australia said.

Federal emergency management minister Murray Watt has offered more troops and said on Monday the government has activated the satellite emergency management system to help with the flood relief efforts.