A tropical low building in the Coral Sea is expected to turn towards the coast from Sunday, with the system most likely becoming a tropical cyclone by Monday.
The Bureau of Meteorology says the system could strengthen to a category three or higher, possibly making a "severe impact" on the Queensland coast.
A bureau spokesman said on Thursday a cyclone could cross the state's east coast from Tuesday but it was too early to predict where it would make landfall.
"The earliest possible is in the latter part of Tuesday but that's not particularly likely," he said.
"We're looking beyond that to get a better idea of when it might actually affect the Queensland coast."
The new danger coincides with a massive clean-up effort finally gaining momentum in the state's far north after record flooding in December caused by Cyclone Jasper.
Meanwhile, a monsoon trough moving slowly over the Northern Territory was delivering damaging winds and heavy rain to Darwin on Thursday.
Warm, humid and stormy conditions forecast for large parts of — Bureau of Meteorology, Australia (@BOM_au) #Qld & north-east #NSW today. Severe storms are expected, with heavy rainfall, flash flooding, damaging winds, & large hail also possible.Latest forecasts: https://t.co/4W35o8i7wJ or the BOM Weather app. pic.twitter.com/F3zMe8PPqJJanuary 18, 2024
Localised intense falls capable of triggering life-threatening flash flooding were also possible south of Katherine, including at Tennant Creek.
The low is expected to remain inland for seven days as it rolls across the Top End and into Western Australia early next week.
"We're expecting quite a slow movement over the coming days," the bureau spokesman said.
"Over the weekend we expect to start to see it take a bit more of a westward track ... we're going to start to see it pick up a bit of momentum as well so it won't be quite as slow moving once it does start heading to the west."
Warm, humid and stormy conditions are likely across large tracts of Queensland and north eastern NSW on Thursday, with severe storms delivering heavy rain, damaging winds and potential flash flooding.
About 150 properties at Orara River, near Grafton in the state's Northern Rivers region, have been left isolated and could remain cut off for several days but the State Emergency Service is confident it can get supplies to residents where needed.
The agency responded to about 200 incidents statewide between midday on Wednesday and Thursday morning.
Sydney was hit with heavy rain overnight, including 49mm at Penrith and nearly 40mm in the city centre.
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