Record floodwaters that may take days to recede have isolated 17,000 people across northern New South Wales, while the Queensland government has declared a natural disaster in the south of the state.
The ABC reports the cotton capital of Moree in northern NSW has been cut in two by its largest flood in 35 years, and many areas are receiving supplies by air.
Several thousand people are sheltering in evacuation centres as the swollen Mehi River inundates low-lying parts of the town. On Friday morning, the river passed its forecast flood peak of 10.6m, reaching a similar level to that in floods in 1976.
The ABC says the town's 9,000 residents have been separated by floodwaters since the main bridge was closed on Thursday night and homes and businesses have been sandbagged.
The State Emergency Service has 17 helicopters carrying out rescues as well as resupplying towns such as Wee Waa and Narrabri, and down to the coast.
Diana Smith, who lives 20km east of Moree on the Gwydir Highway, told Checkpoint her family had to stay home overnight because they were cut off from evacuation centres.
Disaster declared in Queensland
The Queensland government has declared a natural disaster in the state's south as floodwaters rise and crews continue to rescue stranded residents, the ABC reports.
The inland town of Roma has been cut off, with more than 200 homes under threat despite emergency crews spending much of the morning sandbagging houses and businesses, the ABC reports.
The rain has stopped but Bungil Creek has continued to rise, exceeding an 8.1m level recorded in March 2010.
Private aircraft have carried out some rescues in Roma and stranded families are being boated to safety.
A child has been rescued after a car was swept off a road, but rescuers are still trying to find a woman who is missing.
The town of Charleville could expect a flood peak on Saturday morning that would come within millimetres of the levee that protects the town.
The ABC says people have had to be moved from an evacuation centre that was under threat in Mitchell, east of Charleville, after the Maranoa River reached a record level.
Dozens of homes have been inundated.