Residents in sodden Townsville have been urged to seek higher ground as heavy downpours forced the floodgates to the city's swollen Ross River Dam to be completely opened.
With up to 500 homes are already under water, a heavy deluge of rain on Sunday pushed levels to almost 250 per cent capacity with authorities opening the floodgates, almost doubling the amount of water flowing out of the catchment.
Close to 2000 cubic metres of water was surging out of the dam every second after 9pm on Sunday, prompting warnings from the Bureau of Meteorology to residents in low lying areas.
"You can expect high velocity flows and unprecedented areas of flooding to occur in the Ross River Catchment," BoM spokesman Bruce Gunn said in a video statement.
"It could change continuously and unpredictably over the course of this evening into (Monday) morning."
The Ross River at Aplin Weir was at 3.11 metres and rising late on Sunday night, with authorities expecting it to reach four metres,
The extra water could flood more homes along the river with people in several suburbs including Rosslea, Hermit Park and Townsville City told to move to higher ground immediately.
The monsoon trough that's been dumping vast amounts of rain on the state's north for a week has rewritten Townsville's record books.
In just seven days, the city copped a staggering 1012mm, eclipsing the previous record of 886mm set on the city's so-called Night of Noah when vast swathes of the city went under back in 1998.
Parts of north and central Queensland could get another half a metre to a metre of rain over the next few days.
Authorities have pleaded with Townsville residents who are still in their homes to get ready.
"We don't know when this event will end," Townsville Mayor Jenny Hill said.
"We cannot give you any certainty about what we are going to need to do into the future."
Townsville Airport announced it had cancelled all flights in and out of the facility just after 6pm due to safety concerns.
With water levels at waist and chest height in some suburban streets, local police chief and District Disaster Coordinator Steve Munro said the crisis was only half over.
If things go the city's way, the flood might not affect any or many more than the 400 to 500 properties already inundated.
But he warned: "It could move up to the 10,000, 20,000 (mark). That's the worst case scenario we're looking at if things keep going pear-shaped. We don't want to get to that stage."
The monsoon trough has brought driving rain to other parts of the state too, including drought-hit communities out west.
At Hughenden, properties are facing inundation and the forecast is for more major falls out there, as far as Mount Isa near the Northern Territory border.
Back on the east coast, communities from Ingham to Mackay, 500km away, are at risk of flash flooding and damaging winds, including the possibility of tornadoes.
In Townsville, people are sharing dramatic stories of what they had to do to escape fast-rising flood waters.
Hermit Park resident Randall Parker used a blow-up air bed to float his family to safety after water rapidly swallowed his unit.
"It is just unbelievable ... It just keeps bucketing down," he told The Sunday Mail.
"I just had to get the family out including a newborn baby as quick as possible."
Australian Associated Press