Over 32,000 people in Sydney may need to flee amid Australia's worst floods

More than 30,000 residents of Sydney and its surrounds have been told to evacuate or prepare to abandon their homes on Monday as Australia's largest city braces for what could be its worst flooding in 18 months.

Parts of the city of 5 million people are facing a fourth flooding emergency in a year and a half after torrential rain since Friday caused dams to overflow and waterways to break their banks.

The latest information we have is that there's a very good chance that the flooding will be worse than any of the other three floods that those areas had in the last 18 months, Emergency Management Minister Murray Watt told Australian Broadcasting Corp.

The current flooding might affect areas that managed to stay dry during the previous floods, Watt added.

New South Wales state Premier Dominic Perrottet said 32,000 people were impacted by evacuation orders and warnings.

You'd probably expect to see that number increase over the course of the week, Perrottet said.

Emergency services had made 116 flood rescues in recent days, 83 of them since 9 p.m. Sunday, he said. Hundreds more requests for help were made by Monday morning.

Australia's Bureau of Meteorology manager Jane Golding said some areas between Newcastle, north of Sydney, and Wollongong, south of Sydney had received more than a meter (39 inches) of rain in the previous 24 hours. Some has received more than 1.5 meters (59 inches).

The system that has been generating this weather does show signs that it will ease tomorrow, but throughout today, expect more rain, Golding said.

Rain was forecast across New South Wales's coast, including Sydney, all week, she said.

The flooding danger was highest along the Hawkesbury River, in northwest Sydney, and the Nepean River in Sydney's west.

The water is flowing really quickly, Golding said. It's dangerous out on the rivers and we do have some more rain to fall which means the flash-flood risk is not over yet.

State Emergency Services Commissioner Carlene York said strong winds had toppled trees, damaging rooves and blocking roads. She advised against unnecessary travel.

Theresa Fedeli, mayor of the Camden municipality on the Nepean River southwest of Sydney, said the repeated flooding was taking a toll on members of her community.

It's just devastating. They just keep on saying devastating, not again,' Fedeli said.

I just keep on saying ... We've got to be strong, we will get through this. But you know deep down it's really hitting home hard to a lot of people," she added.

Perrottet said government and communities needed to adapt to major flooding becoming more common across Australia's most populous state.

We're seeing these flood events more regularly, there's no doubt about that, Perrottet said.

"To see what we're seeing right across Sydney, there's no doubt these events are becoming more common. And governments need to adjust and make sure that we respond to the changing environment that we find ourselves in, he added.