Swift-water rescuer Michael Plumb is one of 10 Queanbeyan SES workers who have been helping with heavy flooding in Central West NSW, while their ACT counterparts remain on standby to assist if needed.

He said the six-hour stand-off involving emergency services and police was the most challenging rescue he's ever undertaken, because the man stuck on top of his car did not want to be rescued.

"He was in the middle of the causeway and was going to try to walk out because he didn't want to put anyone else in danger by rescuing him," Mr Plumb said.

"We eventually talked him out, but none of the rescuers there had ever been through anything like that."

Queanbeyan SES currently has workers in Forbes, Condobolin and Cowra supporting rescues and helping with flood mitigation efforts.

But back home, SES members in Queanbeyan and Canberra have also been busy preparing for the downpour of up to 45 millimetres on rain on Thursday, expected to add to the damage already caused by months of above-average rainfall.

Queanbeyan SES public information officer Brent Hunter said about 100 workers were preparing to lay sandbags to protect properties and repair leaking rooves while keeping an eye on the Queanbeyan River and Googong Dam, which was almost at capacity on Wednesday afternoon.

An ACT SES spokesman said Canberra had extra volunteers on call to travel interstate and had been running extra training for storm or flood damage responses.

"Canberra is lucky to be a well-planned city, so we don't see as much devastation as other areas around Australia," he said.

"Our flooding tends to be more 'nuisance' flooding where water flows over low-level crossings and sometimes over roads."

He said workers had a "considerably busier year" than usual due to Canberra's third wettest winter followed by possibly the rainiest September on record.

So much wet stuff has taken its toll on Canberra roads, director of ACT roads Tony Gill said.

He had received a 30 per cent rise in reports of pot holes between June and August than in 2015, as well as more residential flooding and stormwater damage.

"Many of our construction projects have also been interrupted," he said.

"Some of the larger government and private development projects have had a three or four-week delay."

Fortunately, Canberra has been spared any flood warnings, but nearby Yass was declared a natural disaster on Wednesday.

Recent storms and flooding had caused hundreds of thousands of dollars worth of damage to roads, sewerage, water-supply equipment, buildings and parks.

The declaration makes Yass Valley Council one of 21 local governments to receive disaster relief funding from the NSW government.

The ACT SES has the following advice for Canberrans to cope with the upcoming wet weather: