It's the wettest December in more than 150 years in parts of Queensland, where flooding has cut off many rural towns and is seriously damaging sugar cane and wheat crops.
Army helicopters have been called in to evacuate people from their homes in several areas and many roads are closed.
The entire population of Theodore - 300 people - has been evacuated, and helicopters are due to go in to fly out pets left behind.
Residents in parts of the coastal city of Bundaberg are being asked to leave their homes ahead of the expected peak of floodwaters overnight. Dozens have already left their homes.
Local officials say that although rain is now clearing from some regions, flooding is still a major threat, and river levels are expected to remain high for several days.
A prominent economist, AMP's Shane Oliver, says the flooding in Queensland and northern New South Wales could cost the national economy billions.
Mr Oliver says crop damage and delays in coal shipments will have an impact of about 0.5% on GDP, which is "quite a sizeable impact".
Ian Burnett of the rural lobby group Agforce says the agricultural recovery will be slow.
"We've got some areas that have had two or three events in the last two years," he says, "so there's a real cumulative effect."