A man in his 60s has been found dead in a car submerged in floodwaters in southeast Queensland, taking the state's death toll for the disaster to 12.
His body was found late on Sunday night in Wondai, in the South Burnett Region, the Queensland Fire and Emergency Service confirmed on Monday.
A woman, also in her 60s, who was a passenger in the car, managed to get out and was found clinging to a tree.
In NSW, a severe weather warning has been issued for the east with intense and heavy rain expected to cause more inundation in already saturated and flooded areas.
The Bureau of Meteorology warning covers the entire coast from Coffs Harbour in the north to Bega in the south.
There is the chance of a thunderstorm, large and powerful surf as well as flooding that may reach levels similar to last week.
"Heavy rainfall will persist throughout the warning area today, with the peak of the rainfall most likely about the Sydney Metropolitan and Illawarra districts later tonight and into Tuesday," the BOM said.
The heavy rain could lead to flash flooding in Sydney, Mid-North Coast, Hunter, Illawarra, South Coast, and parts of the Tablelands.
Six-hourly rainfall totals between 70mm to 120mm are possible on the east coast on Monday.
"Thunderstorms may deliver heavier totals over short time periods," the BOM says.
Multiple flood warnings are current for parts of NSW, with the Hawkesbury and Nepean regions in danger of more moderate to major flooding.
The BOM has observed renewed rises on multiple rivers and warns that flooding may reach levels similar to the past week.
Thunderstorms could also bring intense rain to the Northern Rivers. Damaging winds and large hail could hit Lismore and nearby towns which are trying to clean up from last week's devastation.
The flooding has claimed six lives, including four in Lismore.
Rescue efforts continue
The State Emergency Service (SES) had another 550 calls for help overnight and performed nine flood rescues.
SES Deputy Commissioner Daniel Austin says volunteers are waiting with "bated breath" to see what the latest east coast low brings.
"We're certainly on high alert from the Mid-North Coast down into the Shoalhaven," he told the Nine Network on Monday.
"I would expect throughout today that you will see another batch of warnings and evacuation orders potentially for a number of catchments.
"We are watching exceptionally closely a number of catchments that are going to come very close to, potentially, tops of levees ... around the Hawkesbury and Central Coast and places.
"The water hasn't retreated yet. We're now going to see more flooding on top of what we've already seen."
Across the state, rain is causing significant travel delays with cancellations expected on most Sydney Trains, NSW TrainLink Intercity and Regional trains services on Monday.
Commuters are being advised trains will run to a changed timetable and to allow extra travel time and avoid non-essential travel.
Drivers are also being told to avoid non-essential travel on the roads.
No reprieve for Queensland
Overnight on Sunday, Queensland's southeast was again lashed by heavy rain, with hail reported in Logan.
Almost 80mm of rain fell in Brisbane which was deluged last week when the Brisbane River rose above its banks.
The Bureau of Meteorology has forecast more severe storms and damaging winds for eastern parts of Brisbane, Ipswich, Logan and Gympie during Monday.
The damages bill for the disaster is expected to be more than $1 billion, including insurance claims and major infrastructure repair, but the final number is still to be determined.
"For an event that lasted just three days, it's going to have a big impact on our economy and on our budget," Treasurer Cameron Dick said on Sunday.
There are still 140 people in evacuation centres and thousands of homes still without power.
"This has really packed a punch, these floods have had a big impact on people and it's going to take not just weeks but months for people to recover," Premier Annastacia Palaszczuk said on Sunday.
Meanwhile, the state Labor government has donated $2.1 million to charitable groups supporting flood survivors.
The donation includes $500,000 each to the Australian Red Cross, Lifeline, The Salvation Army and Vinnies, and another $100,000 to GIVIT.
Ms Palaszczuk said the organisations had a track record of getting money to where it's needed.
