Extreme weather driven by tropical cyclone Jasper has dumped a year’s worth of rain on some areas.
Images show planes stuck on Cairns airport runway, and a 2.8m crocodile captured in floodwaters in Ingham.
Authorities called off the evacuation of Wujal Wujal’s 300 residents due to adverse conditions.
No deaths or missing people have so far been reported.
However, authorities expect the flooding to be the worst recorded in the state, and intense rainfall is expected to continue for another 24 hours.
Hundreds of people have been rescued – with many homes inundated, power and roads cut off and safe drinking water dwindling.
The city of Cairns has received more than 2m (7ft) of rainfall since the weather event began.
Its airport was closed after planes became trapped by flooding of the runway, although authorities say the waters have since cleared.
Queensland Premier Steven Miles told the Australian Broadcasting Corporation (ABC) that the natural disaster was “about the worst I can remember.
“I have been talking to Cairns locals on the ground… and they say they have never seen anything like it,” he said.
“For someone from far north Queensland to say that, that is really saying something.”
Rain thwarts evacuations
In the remote town of Wujal Wujal, about 175km (110 miles) north of Cairns, nine people including a sick child spent the night on the roof of a hospital after emergency crews were unable to reach them.
The group were relocated to another spot on Monday, but Mr Miles said he had been forced to call off the evacuation of the rest of the town due to the bad weather.
Another attempt would be made on Tuesday morning local time, ABC reported. All those remaining were “safe and on higher ground”, said Queensland’s Deputy Commissioner Shane Chelepy.
Mr Miles had earlier voiced “concerns about drinking water, about sewerage, power and telecommunications, the roads – many of the roads are blocked and we can’t get aerial support in”.
Forecasters said the torrential rain would continue for most of Monday and coincide with a high tide, intensifying the impact on low-lying communities.
While the rain is expected to begin easing on Tuesday, rivers are yet to peak and will remain swollen for days.
Several rivers are expected to break records set during a flood event in 1977. The Daintree River, for example, has already exceeded the previous record by 2m, after receiving 820mm of rain in 24 hours.
State officials estimate the toll of the disaster will top A$1bn (£529m; $670m).
Eastern Australia has been hit by frequent flooding in recent years and the country is now enduring an El Nino weather event, which is typically associated with extreme events such as wildfires and cyclones.
Australia has been plagued by a series of disasters in recent years – severe drought and bushfires, successive years of record floods, and six mass bleaching events on the Great Barrier Reef.
A future of worsening disasters is likely unless urgent action is taken to halt climate change, the latest UN Intergovernmental Panel on Climate Change (IPCC) report warns.
Source: BBC