More than 238,000 households and businesses are without power as ex-Tropical Cyclone Alfred dumped heavy rain across large parts of south-east Queensland and northern NSW while moving inland.
A new severe thunderstorm warning was issued early on Monday for parts of Ipswich, Logan, Scenic Rim, Sunshine Coast, Brisbane City and Moreton Bay Council areas.
The Bureau of Meteorology has warned of intense rainfall that may lead to dangerous and life-threatening flash flooding, particularly along the Bremer River and Warrill and Laidley Creeks.
Residents have been told to move to higher ground away from the water or get ready to leave immediately if the threat worsens.
"If you are near flood waters, get up as high as you can where you are," Queensland Police said on Monday.
In northern NSW, rain is falling, roads remain closed and people are being warned not to drive through floodwaters.
Some 1,800 people have been isolated by the deluge and another 18,500 have been told they're at risk.
Across the north-east, 20,300 people have been told to evacuate.
Over the weekend, some residents were allowed to return to their homes in places such as Lismore as conditions eased.
NSW SES assistant commissioner Sean Kearns said on Monday: "We're not out of the woods just yet."
"The predicted risk of heavy rain to continue throughout Monday and possibly into Tuesday will only exacerbate this risk."
One dead, 13 soldiers injured
Prime Minister Anthony Albanese is in Lismore on Monday and is expected to hold a press conference.
He flew into Brisbane on Sunday as flooding shut down a Queensland community and falling trees destroyed homes and cars.
Residents at Hervey Bay north of Brisbane were told to stay inside under an emergency declaration after almost 250mm of rain fell in hours, triggering flash flooding.
Parts of Gold Coast received an emergency warning late on Sunday, with communities told to "take action now" and stay off the roads.
"If you are near floodwater, you may need to get up as high as you can to survive," the warning said.
The Gold Coast and northern NSW have felt the brunt of the severe weather, recording gusts of 100km/h. Source: AAP / Dave Hunt
But some were not so fortunate with confirmation a body had been found, believed to be a 61-year-old man after his ute was swept into floodwaters at Megan, near Dorrigo, NSW on Friday.
Thirteen soldiers were also injured, including two who remain in a serious condition after a truck accident near Lismore, NSW on Saturday.
Defence Minister Richard Marles said on Monday the circumstances of the accident were still being investigated.
Some schools re-open
Queensland Premier David Crisafulli said schools would re-open in south-east Queensland on Monday "where it's safe to do so".
More than 1,000 schools were closed last Thursday, and 685 remain shut.
"If getting to school from your particular property isn't safe, well of course that's a decision parents will make and they will be supported in that, I can assure you.
"Where it's safe to do so, those schools will open."
