The Glenelg River at Casterton reached major flood levels overnight on Saturday and into Sunday, rising almost half-a-metre within 10 hours, to 6.10 metres about 4.30am.

State Emergency Service media officer Bruce Farquharson said the water level had barely dropped since it's overnight peak.

"It's been hanging on pretty well, it's only dropped two centimetres since then," he said on Sunday morning.

With rain forecast, the river is likely to remain around six metres during Sunday and into Monday. The Bureau of Meteorology has forecast light showers in the morning, before another rain band moves across bringing between 5-to-15-millimetres of rain, likely causing renewed stream rises.

As of Sunday morning, 10 homes were predicted to be inundated and a further 40 to 50 surrounded by water.

Mr Farquharson said two residents of a house in Racecourse Road had to be relocated about 1.30am. "They took a cautious approach and got out," he said. "They're in alternative accommodation now and are safe and sound."

Another house with a single occupant in McKinlay Street was evacuated later on Sunday morning.

"We expect the water will take about 24 hours to recede to the point where houses are able to be accessed for inspection," Mr Farquharson said.

He said about 45 Casterton residents attended a community meeting held on Saturday afternoon.

"The Casterton community knowns floods, they've had many floods over the years," Mr Farquharson said.

The Casterton Races were called off this morning. Casterton Racing Club manager John Donnelly said between 600 and 700 horses were expected at the jumps track on Sunday for the club's annual spring meet.

Mr Donnelly said the track's turf was unaffected, but the club's two access roads were blocked.

"This has happened before, in 1991, so if it only happens every 25 years I don't think we'll complaint too much about it," he said, despite the event bringing an economic boost to the small town.

Glenelg Inn publican Troy Robbins said floodwaters came within metres of the hotel. "It peaked here about 3.45am out the front of the pub, so we didn't have any water inside," he said.

Meanwhile SES Dartmoor members came to the aid of a milk tanker that had become trapped in quickly rising water early on Sunday.

SES Dartmoor controller Dallas Oakley said the driver had to be rescued by boat about 1am. "He decided to drive through floodwater and got stuck," he said.

It took about half-an-hour to rescue the tanker just outside Casterton.

Further upstream, the township of Harrow is bracing for flooding of its own. The SES's Bruce Farquharson said the Harrow Mechanics Institute Hall was impacted, but there were few other buildings in town subject to flooding.

The Bureau of Meteorology issued a major flood warning for the Glenelg River on Saturday night.

Twelve properties were expected to flood, while Murray and McPherson streets were predicted to flood to more than half a metre.

The SES has advised Casterton residents not to walk, ride or drive through the floodwater, keep children away and to stay well clear of waterways, stormwater drains and fallen power lines.

Sandbagging was under way and a community relief centre set up at the Casterton town hall on Saturday.

The Glenelg River last flooded Casterton in 1996.

Residents in the nearby town of Coleraine were evacuated on Friday night, with tiger snakes seen swimming through the streets to escape the rising water.

Elsewhere in the state, a moderate flood warning has been issued for the Murray River at Corowa and a minor flood warning for the Murray River at Albury.

Current Emergency Information is available at Vic Emergency.

For emergency assistance contact the SES on 132 500.

Current road and traffic information is available at the VicRoads website.