The city of Bundaberg is of most concern on Tuesday, with 2000 people in evacuation centres and 2000 properties affected by flooding.
There are ongoing concerns that houses could be swept from their stumps as torrents of water course through swathes of the city.
Overnight, a fleet of 14 helicopters rescued more than 1000 people from Bundaberg's northern suburbs, and missions are expected to continue on Tuesday.
"There may still be people in there and we have to get them out," Premier Campbell Newman said on Tuesday morning.
Planning is also well advanced for the evacuation of more than 100 patients from the Bundaberg hospital amid concerns it could lose power. They will be flown to Brisbane hospitals.
But the city of Ipswich, west of Brisbane, appears to have been spared damage after the Bremer River peaked at 13.9 metres on Monday evening, well below the predicted 15 metres.
"People are going to wake to the most joyous news,'' said Ipswich councillor Paul Tully, adding that not one of the 600 homes and businesses evacuated in suburban Goodna had gone under.
Meanwhile, the expected flood peak in the Brisbane CBD in coming days has been revised down slightly.
Minor flood peaks, coinciding with high tides, are expected on Tuesday, Wednesday and Thursday.
The most significant is expected to be 2.3 metres but possibly up to 2.5 metres, about 11am (Australian time) on Tuesday, the Bureau of Meteorology says. The previous forecast was for 2.6 metres.
Some low-lying suburbs have already experienced flooding, and authorities say up to 5000 businesses could be affected by some level of inundation.
But Brisbane Lord Mayor Graham Quirk says the peak will be two metres lower than it was in 2011.
"The city will be open for business," he told ABC radio.
However, floodwaters have breached levee banks in the city of Maryborough overnight, and it's believed some homes and businesses may have been inundated.
Fraser Coast Mayor Gerard O'Connell said the Mary River peaked at 10.65 metres at 4am (AEST) on Tuesday and inspections were underway.
"The water is creeping into homes and businesses but I think most people were able to expect that," he told the ABC.
In the Darling Downs town of Warwick, southwest of Brisbane, there are hopes most homes and businesses have escaped flooding after the Condamine River peaked overnight half a metre lower than predicted.
Mayor Peter Blundell hopes the lower peak will have saved about 60 homes and businesses that were at risk of having water above the floorboards.
But up to 40 properties would still have had some form of inundation.
"How many had water into their living areas, we're not sure," he said.
Energex says 160,000 customers are still without power across the state, and 1100 power lines are down in the southeast.
The State Emergency Service had received 3400 calls for help in the 24 hours to 5am on Tuesday.
Most jobs were in central Queensland, the north coast, Brisbane and the wider southeast region, for evacuations, sandbagging and roof damage.
A total of 46 council areas are now eligible for government assistance, including Brisbane City, the Gold Coast, Logan, Redland, Scenic Rim and South Burnett local government areas.
After hitting the Hunter on Monday evening, the front was expected to hit Sydney around dawn on Tuesday, he said.
"We're expecting really damaging winds of up 100km/h; we're expecting torrential rain of up to 100mm and possibly 200mm in localised areas," Mr Pearce said.
"We're expecting flash flooding, we're expecting trees to be brought down, wires to be brought down by these winds.
"We're expecting a very challenging 24 hours in front of us."
On Monday, about 1500 residents downstream of Grafton were ordered to leave their homes in Ulmarra, Cowper and Brushgrove districts.
Floodwaters have also cut off all roads between NSW and Queensland.
FLOOD TOLL RISES TO FOUR
A three-year-old boy injured by a falling tree has died in hospital, taking the total number of people killed by Queensland's flood disaster to four.
The young boy and a 34-year-old woman suffered head injuries when a tree fell on them at Gordon Park, in Brisbane's north, on Monday morning.
Queensland police have released a statement saying he had died in Royal Brisbane Hospital.
Initial information suggests that the woman and three-year-old boy were standing on Kedron Brook bikeway when they were struck by the tree about 8.30am.
They were both taken to hospital in a critical condition.
Police will prepare a report for the coroner.
In other incidents, a motorcyclist's body was pulled from the Oxley Creek, south of Brisbane, on Monday.
He was seen being swept from his bike at Greenbank at Logan late on Sunday night.
An 81-year-old man's body was also pulled from the water near Bundaberg and a 27-year-old man died when he tried to cross a flooded creek near Gympie.
RACE ON AGAINST RISING FLOODS
The race was on to rescue 1500 people from parts of Bundaberg last night, with the Queensland Premier warning that torrents of water could wash houses away.
Campbell Newman said aircraft were being scrambled to get people out of north Bundaberg and other low-lying areas.
The city has been hit by a record flood, with about 2000 properties already affected by flooding last night and waters still rising.
Two defence force Blackhawk helicopters were part of the operation, which involves at least 14 aircraft.
The speed of water through some parts of the city was estimated at 40 knots, or almost 75km/h.
"The velocity of the water, and the rises in the water levels, means that houses, particularly in north Bundaberg, and maybe other locations, could be swept away," Newman said.
Mandatory evacuations were affecting about 5000 people in Bundaberg. The Burnett River is at record levels. It could reach 10m today.
Newman said Bundaberg was at the centre of the emergency response, but with so many other communities also affected the tempo of the state's latest disaster was rising.
Late last night, residents of Warwick were anxiously watching the rising Condamine River, with 30 homes already flooded and more expected to go under.
The river had cut the town in two and about 180 people were in evacuation centres.
If the forecast peak of 8m occurred, 92 more houses and 17 businesses were expected to be flooded.
Ipswich was starting to flood, with some businesses in the CBD under water after the Bremer River broke its banks. Up to 350 properties could be affected.
Hundreds of people streamed into an Ipswich evacuation centre before the flood peak of 15m.
Some parts of Brisbane were already flooded, with a flood peak in the Brisbane River due this afternoon.
About 5000 homes and businesses could face some flooding but the damage in Brisbane and Ipswich would not be anything like it was in 2011, the Premier said.
Three people have died in Queensland: a motorcyclist whose body was pulled from the Oxley Creek south of Brisbane, an 81-year-old man whose body was found near Bundaberg, and a 27-year-old man who tried to cross a flooded creek near Gympie.
In other developments yesterday:
Four hundred dairy cattle were washed away at Mundubbera, southwest of Bundaberg.
The wild weather whipped up layers of ocean foam, blanketing some roads and parks on the Gold and Sunshine coasts. The white froth came up the foreshore at Burleigh Heads and was covering pedestrian paths and picnic areas. In some places the suds were up to 1m high.
The low-pressure system has now crossed the New South Wales border, bringing 1400 calls for help and more than a dozen swift-water rescues.
Floodwaters have isolated thousands of NSW residents and caused evacuations in the state's north, as the storm beats a path towards Sydney.
About 2000 people were cut off in the state's drenched north, with about 850 people isolated at Ewingar, west of Lismore, and 400 at Darkwood, on the Bellinger River.
Flood warnings were in place for eight NSW river systems, the Bureau of Meteorology advised.
Heroic rescues amid destruction
This young boy was plucked to safety from a raging river in Queensland - one of several heroic rescues over the past four days in Queensland. But the drama didn't stop there.
After the boy was rescued, the Swift Water Rescue officer was himself swept downstream in the raging Frenchman's Creek in Rockhampton, and needed to be saved.
In another case, a helicopter crew rescued a family of seven after the family's house was flooded. Those saved were a "grandma, mum, dad, four children - from a one-week-old infant to 16," a rescue helicopter spokesperson said.
Later, two parents and their seven-month-old infant were plucked from a roof of a two-storey house.
Rescuers also airlifted a toddler in a bag and two women after their truck was submerged in floodwaters.
Help from the air in Qld
* Family of seven, including a grandmother and infant, driving in a ute from their Maryborough home to high ground
* Mother, father and 7-month-old infant winched from the roof of a house at Pioneer's Rest
* Elderly man and his 17-year-old dog rescued in North Bundaberg with a crewman securing the dog in a backpack during the winch
* A couple in their 30s winched from the roof of their home in North Bundaberg
* Oxygen-dependent 57-year-old woman airlifted from Gundiah to Maryborough Hospital
* Very ill 70-year-old woman airlifted from Moore Park to Bundaberg Hospital
* Couple in their 60s winched from the roof of their home near Port Bundaberg to an evacuation centre.
- AAP
