On Saturday morning a car tipped over in treacherous conditions on Adelaide Avenue.

The low developing in the Tasman Sea is not expected to create conditions as devastating as those experienced a fortnight ago, but sodden soil could lead to flash flooding in the region.

The Bureau of Meteorology forecasts 10 to 30 millimetres of rain will hit Canberra on Sunday, with five to 15 millimetres following on Monday.

That forecast is well below the 48.8 millimetres the capital received in a single day during the last east coast low.

Conditions will be worse along the south coast, with up to 100 millimetres forecast for Eden and Jervis Bay.

The rain will be heavier in the afternoon as another low brings rain from central Australia during the day, while another low is expected to develop in the Tasman Sea off the Illawarra coast on Sunday night.

That low will move further south on Monday.

ACT State Emergency Service chief officer Conrad Barr said volunteers were on standby in case Canberra again experiences flooding, leaky roofing and other hazards.

He said already drenched soil could contribute to flooding problems if heavy rain struck.

"Our ground is sodden from the last big lot of rain, and so this means that this rain will run off a lot more readily and a lot more quickly than it often does in a rain event," he said.

"The risk with that is some of our low-lying creeks, our river crossings, our causeways and storm water drains may end up with minor to more severe flooding."

A 37-year-old Kambah man died on June 5 after his ute was swept away into Paddys River, below the Cotter Dam.

University of NSW researchers demonstrated how even shallow floodwaters could wash cars away on Friday.

Mr Barr urged motorists to drive to the conditions, avoid flooded roads and stay away from floodwaters and drain pipes.

He also asked residents to ensure their gutters were clear before the rain arrives.

"People can wash away and drown in knee-deep water," he said.

"In this kind of weather, the best thing to do is be at home, warm and dry, not out in a four-wheel-drive in a forest."

Anyone who needs SES assistance can call 132 500, but anyone in a life-threatening situation should call triple-0 first.

The wet conditions are expected to ease from Tuesday, though a strong chance of showers will persist until next weekend.

As the rain eases, overnight temperatures will drop as a cold front passes through on Tuesday, with an expected low of 1 on Thursday.