Further rain expected in the central west of New South Wales could see the Lachlan River at Forbes reach a higher peak, despite it already being inundated with the greatest water levels in 25 years.

NSW State Emergency Service (SES) public information officer Nick Aisake said while the water level in the Lachlan River was slowly starting to go down , it was due to rise again in coming days.

"It's currently at 10.59 [metres] on the Forbes Iron Bridge gauge, now this is giving some reprieve to residents in the township of Forbes," Mr Aisake said.

"However, we are expecting that to rise again and probably above the peak, when the rain arrives late Wednesday into Thursday."

He said 236 properties remained under evacuation order in the town of Forbes and surrounding areas, and it would probably be in place until after the upcoming peak.

"Depending what happens to the water when it does arrive in this rain, it has been a pretty unique flood," Mr Aisake said.

"It will all be dependent on how fast it moves down the stream to Condobolin and they will be assessed on the a day-to-day basis."

SES spokesman Phil Campbell said the focus for the service was the welfare of people in Forbes.

"We still have about 1,000 people that have been evacuated, we're doing assessments to get those people back as soon as we can, as well as ensuring that other communities downstream such as Condobolin are well-prepared as the floodwaters move down river," he said.

Mr Campbell said not all of the people subject to the evacuation orders actually left their homes, even though the SES encouraged everyone to go.

He said the orders remained in place because of the possible further rainfalls.

"We don't want to inconvenience folk by getting them back into their homes, because water levels are at the moment falling, but then with further rain tomorrow night, have water levels rise again and have to further evacuate them."

He said there were about 100 properties isolated at the moment and he asked them to contact the SES.

"The threat is not over at the moment ... we are still mindful of that heavy rain to come," he said.

"We are asking the people of Forbes to make sure they remain vigilant, keep following our instructions and to prepare for further flooding."

Residents may be unable to return home until next week

Forecasters are expecting another 40 to 50 millimetres of rain over the river catchment, Mr Aisake said.

"We are looking at a campaign flood here," he said.

"With the further rain expected it could be into next week before water levels recede enough to allow [residents] to return home."

Forbes Mayor Phyllis Miller said the town was well prepared for more rain, though the forecast could cause more crop damage.

"They looked like having a bumper year, so some have been affected worse than others, depending on whether they're low lying area, so we'll just have to wait and see what the harvest brings," she said.

She said the weather conditions were looking more favourable today and floodwaters had started to subside.

"We're a little bit tired but certainly, if we do get that rain, we'll kick ourselves into gear and keep going," she said.

"There's about 20 [houses] that have got water through them and there's a lot of houses that have water views all around them."