Canberra's dams have reached 90 per cent capacity almost six weeks earlier than expected and may be full by the end of the year, as more wet weather is expected this season.
Both Cotter and Bendora Dams reached 100 per cent capacity at the start of October and Icon Water say Googong and Corin Dams could follow suit by the end of the year.
Canberra's water storage has doubled since Summer when stores dropped to less than 45 per cent.
Googong Dam is currently 88 per cent full and Corin Dam is at 82 per cent capacity.
"Based upon modelling of current forecasts, there is around a 50 per cent possibility that dam levels may reach 100 per cent by the end of the year," an Icon Water spokeswoman said.
"If we continue to see higher than expected rainfall through to the end of the 2020, the likelihood of this will continue to increase."
Dam levels have risen an average of 0.2 per cent per week which increased to 0.5 per cent last week.
The spokeswoman said Canberra's water, which was currently supplied from Bendora and Googong Dams, would be entirely sourced from Googong from November 4 due to works at the Stromlo Water Treatment Plant. This will slow down the rate that dam can hit 100 per cent.
The wet weather expected after Bureau of Meteorology declared a La Nina event last month, will bring more than rain with more storms and flooding expected over the coming months.
SES Queanbeyan operations officer Brent Hunter said people should prepare now by clearing gutters and downpipes and trimming trees and bushes surrounding their home.
"A little bit of water in your guttering can actually start to backflow through into your ceiling, your ceiling insulation sucks it up like a big sponge so it can actually collapse your ceiling," Mr Hunter said.
Although the Canberra region has been spared the downpour which led to flooding further north in the state this weekend, Mr Hunter said there had already been some flash flooding in low-lying parts of Sutton and would be one of the greatest risks this season.
"With these heavy downpours one of the biggest issues we might see is flash flooding our local area," he said.
He renewed the warning that no one should enter floodwaters.
"15cm of fast flowing water can sweep a car off a roadway and put your life in extreme danger," he said.
"I don't think people realise they are not only putting their lives at risk, they're putting our volunteers lives at risk.
"Some people feel they have the car that's capable ... a four-wheel-drive that weighs two tonnes can still get swept off the roadway and we've seen it happen time after time."
Cloudy and rainy conditions were forecast to hang around for the rest of this week but the temperature will start to climb from Wednesday when a top of 19 is expected.
Tuesday will bring a top of 16 and a 40 per cent chance of showers.
Although rain is forecast to be consistent over the next few days it will likely be more sparse than Saturday's deluge.
Up to 6mm is forecast to fall across the next three days, and up to 8mm is expected on Friday.