Two people were missing and the body of a third person was recovered from raging floodwaters as severe storms pounded northeastern Australia on Sunday, forcing more than 1,000 to flee their homes.

Army aircraft were deployed in the northern state of Queensland, where storms generated by former tropical cyclone Oswald unleashed punishing rains and localised tornadoes and floodwaters threatened several major towns.

One woman was plucked to safety in Biloela, 600 kilometres (400 miles) northwest of the state capital Brisbane, after she spent eight hours clinging to a tree.

At Gympie, north of Brisbane, three families waited on the roofs of their homes for seven hours before rescue helicopters, hampered by high winds, managed to reach them, town mayor Ron Dyne said.

A 27-year-old man was missing after he tried to cross a swollen creek near Gympie, and state Premier Campbell Newman said there were serious concerns for another young woman.

"Emergency services are searching for a young woman who reportedly drove into waters near Pacific Haven this morning, and we have grave fears for her safety," Newman told reporters.

Separately on Sunday, police said the body of an elderly man who went to check on a yacht had been recovered from waters north of Bundaberg, where the engorged Burnett River broke its banks and was expected to engulf 300 homes.

Bundaberg was among dozens of towns devastated by floods in Queensland two years ago that claimed 35 lives. Newman said residents there were bracing for the river to peak above nine metres (30 feet), well in excess of the 7.92m seen in 2011.

Further north at Gladstone, about 900 homes were evacuated and several towns in the region were already isolated by the rising waters.

Across the state some 58,000 homes were without power and that number was growing by the hour, according to Newman.

"We are right in the middle of this now, I can hear it bucketing down on the roof as we speak," he said.

Authorities warned residents in New South Wales to prepare for possible flash floods and strong winds of up to 100 kilometres (60 miles) per hour on Monday as the storm system moves further south, the AAP news agency reported.

Prime Minister Julia Gillard said the emergency had revived "memories of the floods of two summers ago", which she said were "still fresh".

The Insurance Council of Australia declared a statewide catastrophe, noting that there had already been "severe inundation... in several towns and cities" and that major flood warnings had been issued.

"Unfortunately, this catastrophe declaration is the result of the first cyclone to come close to the coast this season, and the weather bureau has warned it's highly possible we will see more before the end of summer," said council chief Rob Whelan.

At least one international flight was diverted from Brisbane to Sydney due to the high winds and Qantas cancelled a number of domestic services, with the Sunshine Coast regional airport shut down.

A staggering 1-1.5 metres of rain was estimated to have fallen since the storms began.

Cyclones and floods are common in Australia's northeast during the warmer summer months. A massive inundation of Queensland in 2011 killed 35 people and brought Brisbane to a standstill for several days, swamping some 30,000 homes.

Brisbane was expected to be spared the kind of flooding seen two years ago, with officials predicting 3,600 homes and 1,250 businesses will be inundated, none in the central city.