Victorians are being told to batten down the hatches, with summer thunderstorms threatening to dump mammoth rainfall totals and cause widespread flooding.
While the sun was shining on Saturday, Emergency Management Commissioner Rick Nugent warned the state was set for a major rain event on Sunday and Monday.
"We'll most likely receive totals of around 150mm of rain but we could receive upwards of 200mm of rain across the state," he told reporters.
Emergency authorities are preparing for the worst-case rain scenario and have urged Victorians to do the same, particularly if they live in flood-prone areas.
"Especially people staying in caravan parks and camping along creeks and along waterways," Mr Nugent said.
He said many of the state's rivers and creeks were already quite full from recent rain, making it highly likely the forecast storms could lead to flash flooding in those areas.
"Falling tree branches and flash floods are the highest risk, and please don't drive through floodwaters - you're driving a car, not a boat," Mr Nugent said.
"We don't want emergency service personnel having to rescue people during this event."
Thunderstorms are expected to develop in Victoria's west on Sunday morning, before moving through central, north central and eastern parts of the state during the day and into Monday.
"It's not just a one-day event," Bureau of Meteorology meteorologist Michael Efron said.
He said the low-pressure trough would initially produce widespread rain and thunderstorm activity in the Mallee and Wimmera districts.
Some areas could be set for up to 60mm of rain in less than an hour, he said.
Widespread rainfall totals could be as high as 150mm in central and northern parts of the state, and up to 200mm in the north and northeast.
A warning for minor to moderate flooding has been issued for more than a dozen catchments.
"The amount of moisture across the state at the moment is incredible," Mr Efron said.
"It's what you would normally see in somewhere like Queensland."
In September, the bureau officially declared an El Nino climate pattern, which typically delivers drier conditions for much of the country.
Mr Efron explained other climate factors were influencing the current spate of storms across eastern Australia, including the Southern Annular Mode and above-average sea surface temperatures in the Tasman Sea.
"Those easterly winds are bringing that humid air across Victoria," he said.
"Everyone would have noticed the humidity, and I think we're likely to see that continuing through the rest of this month."
Victoria State Emergency Service chief operations officer Tim Wiebusch said storm fronts with a "tropical moisture link" often spelled flash flooding and subsequent riverine flooding.
Mr Wiebusch said the flooding risk was highest to the state's north but metropolitan Melbourne could face the same threat between midnight on Sunday and midday on Monday.
"We're asking Victorians to get prepared now," he said.
"If you're staying or holidaying in the northeast of the state, or the Loddon or Avoca areas, we would ask you to pay attention to the emergency warnings.
"We've already seen 20 flood rescues from the start of 2024 - that's 20 too many."
SES crews will establish sandbag collection points at high-risk locations such as Bendigo, Castlemaine, Campbells Creek, Heathcote and Wedderburn from Sunday.
Mr Wiebusch said more sandbag sites would be set up.
