Flash flooding is expected to hit parts of Victoria, with authorities warning some people could be isolated for days.
Emergency Management Victoria Deputy Commissioner Chris Stephenson urged communities to prepare early ahead of forecast days-long flooding along river systems.
"You need to make sure that you are prepared for up to 72 hours of potential isolation," Mr Stephenson told reporters on Tuesday.
This includes ensuring any required medication is available, pets are provided for and neighbours are kept in mind. These are important steps because "we need our first responders to actually respond to those vulnerable people, those people that need them most".
"Our volunteers and staff will do everything they can to support and assist communities, but preparing for emergencies is a shared responsibility and it's important that communities do their part too," he said.
The Bureau of Meteorology was expecting widespread falls of 20mm to 50mm across much of Victoria, and higher falls of 60mm to 100mm around the dividing range and northern catchments, many of which are full or overflowing.
"This event is probably the most significant rain event widespread across the state this year, certainly the most significant in recent months," senior meteorologist Kevin Parkin said.
Rain would likely peak on Thursday, along with wind gusts of up to 100km/h affecting elevated locations extending from the Grampians through to the Central Highlands and alpine peaks in the state's northeast, Mr Parkin said.
Watch-and-act flood warnings have been issued for several rivers, with the SES urging Victorians not to camp near streams and rivers this weekend and to avoid driving to northern parts of the state.
"With the weather systems that we're about to see over the next 24 to 48 hours, we are asking Victorians to be flood ready," SES chief operations officer Tim Wiebusch said.
"In particular on Thursday, flash flooding is likely to be a risk in many parts of the state, including urban areas."
Mr Wiebusch reminded residents to plan travel according to the conditions, and advised against travelling on Thursday, if possible.
"Please do not attempt to drive through flood water," he said.
"It's important to understand your flood risk. Find local flood guides for your area on the VICSES website."
Premier Daniel Andrews said emergency services had hundreds of thousands of sandbags on standby, along with seven emergency helicopters and more than 200 generators at the Department of Land, Water and Planning's disposal.
He asked Victorians to be vigilant.
"We know that our catchments are full, we know that we've had record rainfall to this point, and the ground is absolutely sodden," Mr Andrews said.
"Please don't drive into flood waters, (it's) dangerous for you and dangerous for the people who will have to come and rescue you."
WorkSafe health and safety executive director Narelle Beer urged employers to pause outdoor work during heavy rain and storms.
"Temporary fencing, construction tools and scaffold planks can cause serious harm to workers and the public if they become airborne in wild weather," she said.
Dr Beer said powered tools must be stored away in a dry place before rain hits.
"Avoiding exposure to bad weather is the best way to protect yourself and your workers," she said.
