Requests for sandbags and assistance with water damage to properties began around 6.30am as about 100-120 millimetres of rain hit the area before dawn, NSW SES Collector Unit Commander Gary Poile said.

"We went from drought to flood in 24 hours!" Commander Poile said.

There was concern for campers in Gunning's RV park close to Meadow Creek and people began to self evacuate based on the unit's advice as the water rose.

Shortly after, volunteers turned their attention to a farmer who was missing after heading to move sheep to high ground. Fortunately, he was located safely.

"He disappeared from sight for a while with his mob of sheep but it turned out he was fine," Commander Poile said.

The unit also responded to reports of a vehicle stuck in floodwaters on a local crossing.

"They'd managed to get out of the car but that took some tracking down. We worked closely with Collector police," Commander Poile said.

There were also reports of horses stuck in flood waters, which later turned out not to be a major issue.

"The rest of the day we were managing flood waters and school buses and making sure we worked closely with the council to close and open roads," Commander Poile said.

"All up, we had three teams of three, plus myself as controller and it all went pretty smoothly."

The water disappeared as quickly as it came and has now made its way down to Lake George and Burrinjuck Dam, Commander Poile said.

He said the rate at which the water rose was unprecedented for the area, although it wasn't the highest flood the unit has dealt with.

Fortunately, volunteers were somewhat prepared after already responding to calls for help with fallen trees from the weekend's strong winds.

Commander Poile warned of mosquitos and animals displaced from the flood, particularly snakes.

"We're urging motorists to watch out on roads and people not to go playing in flood waters and drains," he said.