An intense week-long wait for Tropical Cyclone Alfred has culminated in death, injury and extensive damage.

Emergency services rushed to the scene of a crash involving two army trucks at Tregeagle, 9km south of Lismore, on Saturday evening.

More than 20 ambulance resources were deployed to help 36 patients.

A number of patients have been taken to Tweed and Lismore Hospitals but NSW Ambulance told AAP not all 36 required transport.

Meanwhile, authorities have also located the body believed to be a 61-year-old man who had been swept away in floodwaters after clinging to a tree for help.

A search had been launched after the man's ute was swept into floodwaters at Megan, about 25 km north of Dorrigo.

He was able to get out of the ute and climb into a tree about 30 metres from the riverbank but was swept away before emergency personnel could reach him.

Senior Meteorologist Miriam Bradbury gives an update on Alfred. – BoM

After extensive search efforts spanning more than 24 hours, his body was found on Saturday afternoon.

In southeast Queensland, residents are still being battered by destructive winds after ex-tropical cyclone Alfred was downgraded, with gusts more than 90km/h recorded on the Gold Coast on Saturday afternoon.

Authorities urged residents not to become complacent as the tropical low became unpredictable and might still bring more dangerous conditions.

Up to 500mm of rain could fall as the remnants of the storm move inland, reaching Dalby by midnight on Saturday and Goondiwindi on Sunday.

The massive rain band stretching across southeast Queensland might lead to life-threatening flooding in coming days, Bureau of Meteorology's Matt Collopy warned.

More than 200,000 people across the southeast and northern NSW remained without power on Saturday afternoon, the biggest loss of power in Queensland's history.

A yacht washed on the shore in the Broadwater at Labrador on the Gold Coast. - AAP

Energex crews were working tirelessly to reconnect homes but it remained a particular challenge on the Gold Coast with the strong winds.

Emergency warnings were cancelled in Queensland but thousands of residents in NSW remained in limbo after evacuating over flood risks.

There has been no loss of life in Queensland but one family was lucky to have escaped injury after four people were rushed to hospital on the Gold Coast due to carbon monoxide poisoning. 

Gold Coast Acting Mayor Donna Gates said it appeared the family had been running a generator inside, sparking a warning for others to keep the devices outside.

Huge waves seen in Coolangatta ahead of landfall. – Kate Simpson via Reuters

Residents in northern NSW's Tweed Shire Council and Bilambil Heights were told to conserve their drinking water and boil any from taps as power outages impact reservoirs.

About 180 Australian Defence Force personnel were on the ground in both states with more on standby.

Shops began to reopen on Saturday across Queensland while Brisbane and Gold Coast airports were looking to reopen on Sunday if safe to do so.

Supermarkets were reopening on a case-by-case basis in Queensland and some public transport would resume on Sunday excluding trains across the southeast and buses on the Gold Coast.

A fallen gum tree is seen impacting a house at Mudgeeraba on the Gold Coast. - AAP

Gold Coast Council urged residents to stay inside after widespread flooding and significant damage across the city, while public transport in the state's southeast remains closed.

There were 29 flood rescues in NSW, mainly people driving through flood waters, and the SES said more than 16,000 people were under evacuation orders.

Prime Minister Anthony Albanese expected there would be "lasting mental health issues" from the natural disaster and vowed to provide assistance.