Rain, thunderstorms and giant hail are forecast for much of the east coast, raising the risk of flash-flooding in areas already reeling from extreme weather.
The Bureau of Meteorology has warned of showers and thunderstorms from northern Queensland, down through New South Wales and into northern Victoria and eastern South Australia into the weekend.
“Heavy rain leading to flash flooding will be the primary risk, with damaging winds and large to giant hail a possibility for inland parts of southern Queensland and inland northern New South Wales, leading to the risk of damage to vehicle and houses,” it said in a statement.
Giant hail was seen last October when freak storms swept over New South Wales and Queensland. It is defined as any hailstone greater than 5cm in diameter and is extremely rare as it can only form under specific conditions.
A low-pressure system is expected to develop over central New South Wales on Sunday night, bringing more rain and storms until Wednesday.
The Bureau said the impact on flood-affected areas would depend on where thunderstorms form and the direction which they move.
There are currently several major flood warnings in place across northern Victoria and New South Wales, with evacuation warnings in place for some communities.
Residents in the northern Victorian town of Kerang have been warned it is too late to leave, after Patchell Bridge on the Murray Valley Highway was closed on Wednesday night.
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Evacuation warnings are still in place for Echuca and the smaller towns of Barmah, Lower Moira and Bunbartha, with swollen rivers threatening to burst their banks.
In Echuca, locals have spent days building a two-kilometre makeshift flood levee through the town to protect thousands of homes and businesses.
On Thursday, the federal government announced an increase of 500 Australian defence force personnel to help with recovery efforts across Victoria and parts of NSW.
In Victoria, up to 400 ADF personnel will assist with various tasks, including sandbag distribution and doorknocking. The remaining ADF members will help out in NSW.
“We’ve already seen our ADF members hard at work filling sandbags in Shepparton, building levee banks in Echuca, and helping out in Wagga Wagga,” the prime minister, Anthony Albanese, said.
“Now they will also be supporting more people as we move to the clean-up phase of this disaster.”
The federal emergency management minister, Murray Watt, said the extra assistance would help some of the nation’s hardest-hit communities.
An emergency warning was issued in Rochester on Thursday morning, alerting evacuated residents that it was not safe to return.
The Murray River is expected to peak on Friday, with concerns it could break the 1993 flood record and reach 95 metres.
Forecast thunderstorms and rain, with falls of up to 30mm, are expected for parts of north central and north-east Victoria from Friday.
Authorities are urging residents to heed the warnings after a second person was found dead in flood waters in Victoria.
The 65-year-old man’s body was found at Nathalia, near Shepparton, on Wednesday morning. His death follows that of a 71-year-old Rochester man on Saturday.
A 63-year-old man has also died in flooding in NSW.