A low-pressure system sitting over central Australia is brewing a significant rain event expected to drag into mid-next week, the Bureau of Meteorology has warned.
Possible severe thunderstorms were forecast for all states and territories on Sunday, with eastern parts of South Australia, western parts of NSW and Queensland's tropical north at higher risk.
More than 50mm of rain had already fallen on the South Australian coastal city of Port Augusta, a welcome change after a hot and dry summer, meteorologist Sarah Scully said.
Six-hourly rainfall totals in the NT could reach as high as 120mm.
Across the four days until Wednesday, Ms Scully said the heaviest rainfall totals of between 150mm and more than 300mm were expected throughout central Australia, Â South Australia's border district, Queensland and NSW.
A "bull's eye" around central Melbourne, with possible falls of more than 75mm, could potentially put out fires burning in Victoria, she said.
Severe thunderstorms and heavy rain are likely in central parts of Australia and northwest NSW on Monday, with flood warnings in place from northern Australia to northern parts of South Australia, extending into Queensland.
Ms Scully said this could create hazardous driving conditions that would disrupt travel as roads were cut off, potentially isolating communities.
"Agricultural impacts throughout central Australia include the threat to livestock and cattle," she said.
"Further south, the agricultural impacts are actually positive, where there's been a lot of people that have been desperate for good rainfall."
The low-pressure system will continue to dig into southeast Australia on Tuesday, bringing severe thunderstorms to central and eastern Victoria, including Melbourne, and western parts of NSW.
Eastern Victoria and NSW are expected to face the bulk of the showers and storms on Wednesday, as the trough finally skirts into the Tasman Sea.
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