Falls of up to 400mm are expected as the storm system makes its approach today and tonight.
North Queensland is bracing for a potential tropical cyclone as the Bureau of Meteorology warns of a "high" chance of development.
Tropical Low 12U is bearing down on the state and currently has a 60 per cent chance to turn into a cyclone.
The Bureau of Meteorology's Dean Narramore said while it was about a couple hundred kilometres north-east of Cairns, its effects were already felt.
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"We've seen the rain already pick up well south of that around the Mackay-Central Coast area where we're seeing widespread rain develop there," he told Today.
"And that rain will continue to develop to the north as we move through today and tonight, as that low gets closer."
The Bureau is forecasting "widespread rainfall" by tonight heading into tomorrow, with falls of 100mm to 200mm, and isolated totals of as much as 400mm.
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Winds are also expected to pick up, with gusts of 80km/hr to 100km/hr into tomorrow.
"The rain is of most concern because we still have a lot of flood warnings current between Cairns and around the Townsville area, and this additional rainfall is going to lead to further and widespread river level rises," Narramore said.
The current warning zone covers Port Douglas to Airlie Beach, including Cairns, Innisfail, Townsville, Bowen, and Proserpine.
Complicating management of the weather event is a serious connectivity issue affecting the Townsville area.
A thief cut a telecommunications line while trying to steal copper in Deeragun.
"My message to that lowlife is you have put at risk the lives of North Queenslanders in their hour of need and you can't get a lower act than that," Premier David Crisafulli said.
"And we intend to make sure that we throw the book at this individual when they are caught.
"Telecommunications are life and death."
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