Alfred has been downgraded to a tropical low after being the first cyclone to hit Queensland's southeast in more than 50 years, but the system is still able to "pack a punch".

About 300,000 homes are without power, a man died in floodwaters and more than a dozen soldiers were injured in a truck accident in the wake of Alfred.

The prime minister flew into Brisbane on Sunday as flash flooding shut down a Queensland community, more were rescued and falling trees destroyed homes and cars with more wild weather to come.

Prime Minister Anthony Albanese thanks armed forces in Brisbane. – AAP

Anthony Albanese said on Sunday that the "situation in Queensland and northern New South Wales remains very serious due to flash-flooding and heavy winds".

"Heavy rainfall, damaging wind gusts, and coastal surf impacts are expected to continue over coming days," Albanese said in Canberra.

Alfred crossed the coast on Saturday but many were caught off guard when strong winds again hit overnight, with gusts up to 100km/h (62mph) recorded in southeast Queensland.

Flooding in Lismore as ex-Cyclone Alfred brings heavy rain. – NSW SES via Reuters

Residents at Hervey Bay north of Brisbane were told to stay inside under an emergency declaration after almost 250mm (9.8 in) of rain fell in a matter of hours, triggering flash flooding and multiple rescues.

"We have certainly seen some heavy rainfall as the system continues to come across the coast – there is no doubt that it continues to pack a punch," Queensland Premier David Crisafulli said.

About 30 rescues took place across Queensland's southeast and northern NSW, with a family of eight driving in rapid floodwaters among those saved.

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.

A tree down in Redcliffe. – BoM

Thirteen soldiers were also injured including two who remain in a serious condition after a truck accident near Lismore, NSW on Saturday.

Prime Minister Anthony Albanese said they were "heroes who were on their way to help people in need".  

In Queensland, roads were flooded and bus services that resumed in Brisbane on Sunday were again suspended as the weather turned nasty.

Rain lashed Hervey Bay, Wide Bay, Brisbane Metro and the Gold Coast hinterland, with 24 hour totals up to 200mm (7.8 in) across Queensland's southeast and northern NSW.

Locals watch the flood situation in the Brisbane suburb of Rocklea. – AAP

An evacuation warning for Lismore's CBD lifted allowing people to cautiously return to their homes, providing some relief for those still reeling from the devastating 2022 floods.

About 15,000 people were under 36 evacuation warnings across NSW, with 800 seeking refuge on Sunday.

NSW's Clarence River is on high alert while multiple flood warnings remain across the state's north.

"This is a fluid situation, the rain is falling unevenly across the catchment and as a result the bit of advice is different for valleys and communities," NSW Premier Chris Minns said. reporters in Lismore.

"Although there are encouraging signs... we're not out of the woods yet."

"One of the big lessons out of the 2025 tropical cyclone compared to 2022 (floods) is pre-deployment, early warning and the most available, accurate information to the public."

Currumbin Beach on the Gold Coast. – BoM

There is no respite with a severe weather warning from Hervey Bay down to NSW's northwest extending to North West Slopes and Plains.

The region is bracing for damaging winds, dangerous surf and 24 hour rainfall totals of up to 100mm leading to flooding.

Showers are not set to become isolated until Tuesday.

"Even after the rain does ease, flooding can continue for several days to come," the Bureau of Meteorology's Jonathan How said.

Brisbane Airport reopened on Sunday but posted online that "ongoing weather may affect the schedule".

A woman surveys the flooding in Lismore. – AAP

Queensland will decide on Sunday on whether around 1000 state schools, closed due to the bad weather, will reopen on Monday, said state Premier David Crisafulli.

"Where it's safe to do so, schools will reopen with the exception of the Gold Coast, where there remains some significant damage, power loss and issues with transport," Crisafulli said.

"One thing's remained consistent, and that is the community spirit and the resolve," he added.

The weather bureau noted the weather system will shift wet weather to coastal parts of NSW by Wednesday and clearing mid to late week.

Southeast Queensland should start to see conditions easing from persistent rainfall on Monday.

Multiple flood warnings remain in effect for the Tweed, Richmond, Wilsons, Clarence and Bellinger rivers in NSW.

Emergency crews rescued 21 people who had driven into floodwaters in the past day, as the SES urged people not to risk their lives by ignoring the strict warnings.

Nearly 50 rescues have taken place so far in the latest flood event.

Beach erosion at Brunswick heads in northern NSW. – BoM