Queanbeyan and Molonglo rivers have been issued a severe weather warning and remain on flood watch.
The Bureau of Meteorology has warned of the chance of flash flooding in the Queanbeyan area. The warning was issued on Wednesday.
Googong Dam is at 99 per cent capacity and may rise further with the rain.
Queanbeyan SES public information officer Brent Hunter said 100 volunteers are prepared to rescue those affected, but urged residents to stay out of flood water.
"It is extremely dangerous and has the potential to take your life," he said.
"Submerged hazards, sewage and other contaminants can end up in the water during floods."
Locals can collect sandbags from 34 Erin Street Queanbeyan to protect their property.
Mr Hunter said residents should clean gutters and secure loose items in yards.
For emergency assistance call the SES on 132 500, and call 000 immediately for life threatening emergencies.
For the latest weather forecasts, rainfall and rain level information, see bom.gov.au.