More than two dozen rescues have been carried out in a 24-hour period, with thousands of people under evacuation orders and two major flood warnings issued.

Mitch Smith spotted the woman in Bendigo Creek at Elmore and swam out to help after her car was swept off a road and washed about 100 metres downstream in raging waters on Monday night.

He secured her to a tree with a strap and the pair waited for about an hour before emergency crews in a boat came to rescue them. Neither was injured.

“The water was probably nine foot, 10 foot deep,” Mr Smith told ABC TV.

“She was pretty exhausted, she said her arms were getting super tired and they wouldn’t be able to hang on for much longer.”

Despite his efforts and praise from police for risking his life, Mr Smith insists he’s not a hero.

“If it was my grandmother in the water I hope someone else would have done the same thing,” he said.

Major flood warnings are current for the Campaspe and Goulburn rivers, with any residents left in Seymour told to immediately evacuate while those in Rochester should shelter in the highest location possible because it is too late to leave.

The flood at Seymour peaked late on Monday and early estimates from the State Emergency Service suggest about 10 homes were flooded and about six in Yea.

Up to 35 homes are expected to be flooded in Rochester on Tuesday, with the town still recovering from devastating floods that impacted about 1000 homes in October 2022.

Rochester Riverside Holiday Park manager Steve Matter said a couple of permanent caravans were flooded by Tuesday morning.

He said there was water on the road out of town and locals were deeply affected by the emergency.

“People are very worried I suppose because they had a flood 15 months ago and now there’s another flood coming,” Mr Matter told AAP.

An evacuation order for Yea has been downgraded but dangerous flood waters remain and is not safe to return.

More than a dozen flood warnings have been issued across the state and the inundation has also impacted Melbourne with most beaches in Port Philip Bay unsuitable for swimming.

The SES has received almost 1700 calls for help since Sunday, with more than 800 related to flooding and 400 for fallen trees.

More than 26 flood rescues were performed in the 24 hours to 7am on Tuesday, with authorities warning motorists to never attempt to drive through flood waters.

Regional V/Line train services on the Seymour and Bendigo routes face major disruptions and cancellations.

The emergency is expected to shift towards Murchison and Shepparton on Wednesday before heading to Echuca.

Murchison post office worker Kirsten Parr said she and other locals were worried roads would be flooded and the town cut off for several days, which happened in the 2022 floods.

“A lot of the houses that did get flooded have just started rebuilding again and now it’s about to happen again,” Ms Parr said.

Victoria SES spokesman Jamie Devenish warned people to be aware of the dangers of “blue sky flooding” as waters continue rising despite fine conditions.

“It might look like a really nice day but that water’s got to go somewhere now and it will push down the catchments and we are expecting to see moderate to major flooding in a number of those communities in northern Victoria over the coming days,” Mr Devenish said.

Some riverine areas are popular for holiday-makers at this time of year and he warned campers in low-lying areas may need to prepare to relocate soon.