(Bloomberg) -- Thousands of people on the outskirts of Sydney were told to leave their homes or prepare to evacuate as days of torrential rain lead to widespread flooding.

With more bad weather on its way, authorities issued dozens of evacuation orders and warnings in Sydney’s southern, western and northern regions. It’s the fourth major flood in New South Wales state in 18 months and the government on Monday warned the latest inundation may be the biggest yet.

“It’s a very worrying situation and could still get worse,” Australian Minister for Emergency Management Murray Watt said on Australian Broadcasting Corp. radio. Some homes that escaped previous floods may be hit this time, he said.

A series of natural disasters in Australia, including bushfires and droughts, has put national climate policy into sharp relief, and a new Labor government vowing tougher action was elected in May. The floods are also triggering fresh debate over where to house a growing population and the cost of insuring homes prone to damage.

Some regions have been swamped with more than 300 millimeters of rain in less than 24 hours, and much of the focus is now on low-lying areas along the Hawkesbury and Nepean rivers, two major arteries that almost encircle metropolitan Sydney.

The Nepean peaked on Sunday, though the Hawkesbury is still rising, threatening communities north of Australia’s biggest city that were flooded just months ago, Watt said. 

Watt said some 6,000 homes are covered by evacuation orders and an additional 12,000 are subject to evacuation warnings. Some 100 defense force troops are on the ground and another 100 have been called up to help, he said.

Areas away from Sydney are also experiencing heavy rain, and the Bureau of Meteorology on Monday issued a severe weather warning for hundreds of kilometers of Australia’s eastern seaboard. The area centers on Sydney but stretches north toward Newcastle, and south beyond Wollongong and Nowra.

Flash flooding is still possible on Monday in Sydney, the Blue Mountains region to the west, Illawarra to the south, and parts of Hunter and the Central Coast to the north, the bureau said. There’s also a risk of landslides, though the rain should clear by late evening, it said.

The stormy weather is stretching a transport system that’s already under pressure from train strikes, a school holiday rush and manpower shortages at airports and airlines.

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