The Lachlan River peaked at 10.75 metres overnight, with low-lying areas of the town expected to flood on Wednesday afternoon.

Emergency Services Minister David Elliott said 275 SES volunteers were stationed in the vicinity and he was “delighted” there had been no flood rescues overnight.

However, he warned people to stay on high alert for rising floodwaters and alert to closed roads.

“It can be many many days before some of these flood waters actually make their way to their final resting place,” he said.

Forbes Mayor Phyllis Miller says residents have been waiting for the flood for almost a week but waters are rising at “a snail’s pace” and she’s concerned people are becoming complacent.

“It’s just a wait and see game. It is awful and people start to get complacent because …. there (are) no signs of flooding and of course, that makes people think that we’re crying wolf,” she told the Nine Network on Wednesday.

“But our river is coming up and it will peak some time today. Every flood is different.

“We’re not sure what that will do inside the town or what will happen with the lake system when that water starts to join up with the river water.”

Some 1800 residents were on Tuesday morning ordered to evacuate by the State Emergency Service, which was concerned the river levels would match or exceed major floods in 2016.

SES Commissioner Carlene York said 800 homes may be flooded, as she pleaded with some reluctant locals to evacuate.

“It’s not unusual for people who have lived in that area and lived through a number of floods to say, ‘it didn’t flood last time, I’ll take the risk and stay’,” she told reporters on Tuesday.

“But every flooding is different and water flows in different ways.”

An evacuation centre has been set up at St Andrews Presbyterian Church for those unable to get to alternative accommodation with family or friends.

Moderate flooding has already occurred upstream at Cowra, and major flooding at Nanami, where the river peaked at more than 12 metres.

Downstream from Forbes, major flooding is also expected at Cottons Weir and Jemalong from Thursday.

The Macquarie, Paroo, Macintyre, Belubula, and Snowy rivers have also flooded over recent days, after parts of the state copped a month’s worth of rain in days.

Six kilometres out of Forbes, on the banks of the Lachlan River, Tom Green has spent the past three days preparing his property, moving machinery to higher ground.

He grows wheat, canola and chickpeas, but with the floodwaters rising upstream, he’s expecting a fifth of his crop to be “written off.”

“We know it’s coming, so we’re preparing for quite a big flood and we’re waiting to see where it peaks but also how much damage it does,” he told AAP.

He said the floods so far looked bigger than in 2016, which caused losses in the district of excess of $200 million.

For Mr Green it’s a “waiting game” with the river not expected to peak at his property until Wednesday or Thursday.

“It could be much worse, but we will wait and see,” he said.

“The sheds are right on the banks there, so we’re packing those up at the moment.”

But he claimed he is a lot better off than others in the valley who will likely experience 100 per cent crop losses.