Residents of Burketown in northwest Queensland are reluctantly leaving their water-logged homes, while emergency services warn that power and sewerage is being cut due to flooding risks.
Police said the last chance to evacuate was during daylight, though several residents have chosen to stay.
Superintendent Tom Armitt told the ABC that emergency services only had a certain window of opportunity to deploy personnel and equipment.
"We don't know how much ground will be left if the water continues to peak and cover all the ground," he said on Saturday.
"If we get to the stage where we are having to shift and move people to rooftops, that makes a whole different level of complexity.
"We don't know when the peak is expected because it has passed any sort of flood modelling at this stage."
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Vision filmed from helicopters shows water covering many buildings to their roofs, with only one or two streets in the centre of the town still untouched.
The town is waiting for its worst-ever floods to peak, with multiple communities and outlying cattle properties isolated as heavy rain leaves the state's west and south at risk of flash floods.
The Albert River at Burketown has already surpassed the record 6.78-metre flood of 2011, and the Bureau of Meteorology said waters in the Gulf of Carpentaria community will likely reach their highest by Sunday.
A forecast for severe thunderstorms and rain in southeast Queensland was downgraded on Saturday, but heavy falls are still possible.
"Sewerage to the town has been compromised and power to the town will be cut off today," police said.
"It is not safe for people to remain."
Weeks of torrential rain have overwhelmed the region's rivers, leaving dozens of communities such as Doomadgee, Normanton and Karumba stranded on islands amid a vast inland sea.
Those towns as well as more isolated settlements and outlying cattle stations are relying on food and other supplies being sent by air and on barges.
The danger of the late-season monsoon has moved south but is expected to weaken at the weekend.
It is expected to bring scattered to widespread showers and isolated thunderstorms to the central and southern districts, with a one-in-four chance Brisbane will receive 60 millimetres.
A severe thunderstorm warning in the Capricornia district was cancelled on Saturday morning after Yeppoon copped 100mm in the hour to 4.11am, and 215mm across the night.
Gladstone received 96mm over two hours.
Seqwater had warned releases from the Somerset Dam into the Wivenhoe Dam on the Upper Brisbane River were possible due to forecast rainfall, however that was later cancelled.
Wappa Dam on the South Maroochy River was spilling on Saturday morning.
Australian Associated Press
