Thousands of Australians were asked to evacuate on Friday after two days of incessant rain triggered flash flooding.
The extreme weather hit the country’s south east, including some in a western suburb of Melbourne as well as large parts of Victoria state, southern New South Wales and the northern regions of the island state of Tasmania.
The areas were pounded by an intense weather system with some receiving more than a month's worth of rain since late Wednesday, officials said.
It is the latest in a series of incidents to have hit Australia, with more than 20 people having died this year with the La Niña weather pattern driving flooding. More than 500 have died in the past three years while billions of animals have perished.
"Our river systems... are reaching major flood levels at various times over today, through the weekend and through next week," Victoria emergency services chief operations officer Tim Wiebusch told reporters.
Many rivers in Victoria, including the Maribyrnong in Melbourne's west and the Goulburn further north, reached major flood levels, prompting the night-time evacuation of residents.
The Goulburn River at Seymour, about 62 miles north of Melbourne, has peaked above the record 25 ft reached in May 1974, data showed. More than 200 flood rescues were conducted by emergency crews.
Upstream in Shepparton, rising flood waters are expected to surpass the 1974 peak by Tuesday and threaten more than 4,000 properties.
"In terms of property damage, road, public infrastructure and the sheer volume of water, this is going to set new records," Victoria premier Daniel Andrews said at a news conference.
Mr Andrews said a decision would be made on Saturday about reopening the state's purpose-built Covid-19 quarantine facility, closed last week after Australia scrapped isolation rules, to shelter flood-impacted residents.
Australian prime minister Anthony Albanese said the federal government stood ready to provide assistance to the flood-stricken states.
"There are already Australian Defence Force personnel on the ground in Victoria ... this is a difficult time, my heart goes out to those communities affected," local media quoted him as saying.
