The 65-year-old man was last known to be on a tractor on a property off Blacksmiths Road at Nathalia on Tuesday afternoon, police said.

A search was begun about 10pm when he failed to return home and the unoccupied tractor was found in floodwaters.

A family member found the man's body in floodwaters on Paynes Road about 8.45am on Wednesday, police said.

The exact circumstances are yet to be determined, but it is not being treated as suspicious.

His death follows that of a 71-year-old man found in the backyard of his Rochester home on Saturday.

With the floods hitting prime agricultural areas, the state government has announced a $73.5 million relief package to help farmers and business owners clean up, including $10,000 grants for primary producers.

"It's pretty overwhelming thinking about what's occurring and has occurred in some of these communities. So any support we provide is really important," Premier Daniel Andrews told reporters on Wednesday.

Small business owners whose livelihoods have been affected may be eligible for a one-off support payment of $5000.

Victorians experiencing mental health struggles as a result of the floods may be entitled to assistance via a $4.4 million healthcare package.

Waters in parts of the state such as Shepparton and Rochester continue to recede and the threat of heavy rainfalls during forecast thunderstorms in coming days has eased slightly.

"Today, we're just expecting thunderstorms in the far north-west of the state. No rainfall across the flooded areas in the north or in central parts," Bureau of Meteorology senior meteorologist Kevin Parkin told reporters on Wednesday.

Showers and thunderstorms on Thursday are now expected to be across the northern districts, but activity isolated.

On Friday and Saturday, widespread showers will generally see totals of two millimetres to 10mm, but higher falls of 30mm could happen in north-central parts and north-eastern parts of Victoria.

"We'll be watching that thunderstorm activity pretty closely and issuing warnings for more of a flash flood risk rather than heavy rainfall over a wider area," Mr Parkin said.

Evacuation warnings are in place for Echuca and the smaller towns of Kerang, Barmah and Lower Moira, with the Murray likely to start peaking on Wednesday.

At Echuca, there are concerns river levels could reach 95 metres, higher than the 1993 floods, by Friday.

Despite the evacuation orders, Echuca is a hive of activity as dozens of people prepare sandbags in the centre of town, while others prepare their homes.

Residents have spent the past few days building a makeshift, 2.5-kilometre flood levee from sand and sandbags to protect thousands of homes and businesses.

However, the wall has divided the town in two, leaving properties and people on the wrong side susceptible to being inundated.

Many people who live along the Murray are hoping a flood levee being built to save the town from the worst of the floods will protect their homes.

One resident told AAP she was grateful the levee was built but extremely concerned if the waters ran over the dirt wall sending privately owned houseboats parked along the Murray into her property.

State Emergency Service chief operating officer Tim Wiebusch defended the wall, saying it was developed by the incident controller, catchment management authority, local government, Victoria Police and others.

"Yes, that will see a small number of properties outside of that levee also potentially be impacted," he said.

Flood warnings are also in place for towns along the Loddon, Campaspe and Goulburn rivers.

On Wednesday, a 3.4 magnitude earthquake sent a shudder near Mansfield, with no reports of damage.

Australian Associated Press