The woman became trapped in the vehicle with two other people on Surprise Creek Rd at Mount Ossa, north of Mackay, about 5am on Wednesday.
The two others escaped from the car, but the woman's body was found a short time later.
The Queensland Ambulance Service said one of the people who survived was treated for a cut to their head.
Queensland Fire and Emergency Services received more than 90 calls for help in the state's north as six-hour rainfall totals reached 240mm in some areas by 1am on Wednesday.
"Although rain is expected to move off the coast in the state's north today, a large number of roads remain flooded," QFES said in a statement.
"Please avoid unnecessary travel and don't risk it on flooded roads and causeways.
"If it's flooded, forget it."
Rainfall records tumbled at the Hughenden, Richmond and Cloncurry airports on Tuesday as those inland regions recorded their highest May totals ever.
Townsville is set for totals upto 250mm on Wednesday and Thursday with the severe weather warning indicating up to 200mm in a six-hour period.
"That whole area under the severe weather warning could see flash and riverine flooding," Bureau of Meteorology senior forecaster Laura Boekel said on Tuesday.
A flood watch is current for dozens of river and creek catchments across Queensland and almost 300 roads have been cut by floodwaters.
In the southeast, heavy rain hit the Sunshine Coast and northern Brisbane, with 135mm falling at Mapleton and 113mm at Maleny.
"If you are on the road this morning take extra care and plan your drive. If you come across floodwater, back it up and find an alternate route," QFES said in a Facebook post on Wednesday.
"With the ground already saturated and further heavy rainfall possible there is a risk of flash flooding today and over the coming days."
Seqwater has alerted Moreton Bay region residents it has started flood releases from North Pine Dam, with releases also set to start from Wivenhoe and Somerset Dams into the Brisbane River from 10am.
The utility expects the releases to flood Savages Crossing, Colleges Crossing, Burtons Bridge and Kholo Bridge downstream, but not Fernvale Bridge.
"If you are downstream of the dam, stay away from fast flowing or deep water near waterways and floodplains," Seqwater said.
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