Flooding in northeastern Australia has caused thousands of homes to lose power and prompted authorities to start evacuations, a year after deadly floods devastated the region.

Homes were evacuated on Brisbane's northern outskirts as Australia's third-largest city was hit by heavy rain, reports said, and authorities urged more people to leave their homes.

Almost 10,000 homes were blacked out and rising waters forced the closure of roads in Brisbane, which ground to a halt for several days in early 2011 due to flooding.

Last year's floods inundated tens of thousands of homes, wiped out huge tracts of farmland, crippled the coal mining industry and killed some 35 people. It was followed by a top-strength cyclone, which worsened damage.

In Brisbane, a waterfront childcare centre had to be evacuated, and three people swam to safety after their car was flooded, television network the ABC said.

Authorities began draining two of the city's dams and said they would likely drain more as the rainfall continued, as meteorologists warned there was more bad weather to come.

"Heavy rain which may lead to flash flooding is expected... over the remainder of today and during Wednesday, particularly about the coast and adjacent inland parts," the Bureau of Meteorology warned.

Northeastern Australia is braced for another exceptionally wet summer season (December-February) due to a La Nina weather pattern in the Pacific Ocean, though the weather is not expected to rival last year's wild storms.

La Nina is characterised by unusually cool ocean temperatures in the eastern equatorial Pacific and has been associated with strong rainfall in Asia and Australia.