Millions of people across southeast Queensland are sweating on Cyclone Alfred's arrival after the category two system stalled overnight.

Alfred is set to cross Queensland's coast near Caboolture north of Brisbane as a category one cyclone on Saturday morning, 24 hours later than initially predicted.

It will be the first cyclone to impact Queensland's southeast since 1974 – when it finally arrives.

Tropical Cyclone Alfred's slowdown will provide no respite, with the delay ensuring heavy rain and massive surf will hit southeast Queensland and northern NSW for longer.

Winds and rain from Alfred's tail are already hitting northern NSW. – Reuters

NSW Premier Chris Minns said Alfred was like an "unwanted house guest" for arriving late and then hanging around for longer, with 24 communities in the state's north preparing to evacuate.

The system is set to trigger wind gusts up to 155km/h and 800mm of rain into the weekend from Brisbane to NSW's Northern Rivers when it eventually arrives.

The weather began to worsen on Thursday with gusts of 96km/h at Cape Morton north of Brisbane and a 12m wave off the Gold Coast.

An emergency warning has been issued for North Stradbroke Island and other islands in the Redland City Council area for destructive winds from 4am on Friday.

Schools, offices, public transport and the Gold Coast airport were closed as Queensland's southeast bunkered down, expecting heavy rain and gale force winds as Alfred approached.

Prime Minister Anthony Albanese speaks to the media at the National Situation Room in Canberra. – AAP

However many in Brisbane woke up to blue skies after the category two system stalled.

Alfred's delay gifted many extra time to prepare, with sandbagging sites reopening for last-minute preparations.

"This system will provide a challenge but if you do the preparation it is a system you will be able to handle," Queensland Premier David Crisafulli said.

Crisafulli called for common sense after reports of people falling off rock walls and playing in the Gold Coast's massive swell, with two people hospitalised.

Wild weather has already hit the coast from Coolangatta down to Ballina in NSW.

About 20,000 properties in the Brisbane area alone are in danger of flooding.

Alfred is sitting off the coast of Brisbane. – windy.com

Destructive winds are set to impact bayside and coastal communities when Alfred finally arrives, with heavy rainfall leading to flooding in Queensland's southeast and northern NSW.

Alfred will also trigger significant coastal erosion, the Bureau of Meteorology's Dean Narramore warned.

Alfred's slowdown has ensured a more prolonged period of significant waves, with a 10m monster already recorded offshore.

"That energy is going to continue to impact all of our beaches in northeast NSW and far southeast Queensland leading to major coastal erosion," Narramore said.

Alfred's delay also guarantees a longer period of heavy rainfall particularly in northeast NSW.

Major flooding is likely for many northeast NSW rivers and possibly in parts of Queensland's southeast, Narramore said.

Cyclone Alfred approaches Australia in satellite timelapse footage. – Reuters/CSU/CIRA & JMA/JAXA

Heavy falls have already been recorded south of Brisbane, NSW's Northern Tablelands and near the Queensland border.

NSW's Northern Rivers is expected to be one of the hardest hit, with about 2000 SES volunteers bolstering the region.

"(Cyclone) Alfred is behaving like a completely unwanted house guest," Premier Minns told reporters in Lismore.

"Unfortunately that means the window for destruction in our community, heavy rains, winds, powerful surf is longer than we would have otherwise liked.

"Prepare for the worst and hope for the best."

Coles and Woolworths stores in areas set to be impacted in southeast Queensland and northern NSW began closing on Thursday.

Commercial airlines have suspended services from Brisbane while Carnival Luminosa's three-day cruise has been called off and Greyhound bus services have been cancelled.

The federal government has activated Australian Defence Force assistance and local council disaster grants.

People collect sandbags in Brisbane as Cyclone Alfred approaches. – AAP

The NSW State Emergency Service has issued 24 prepare to evacuate orders in the Northern Rivers, including towns such as Ballina, previously devastated by record-breaking floods three years ago.

Acting Chief Superintendent Stuart Fisher said the weather events could be worse than the 2022 floods that smashed the region.

"I cannot stress enough this is a significant weather event, not like 2022, where we had a single event," he said.

Rainfall of 700mm is expected to hit the region with authorities stressing to "pray for the best but prepare for the worst".

More than 2000 emergency volunteers armed with drones, high clearance vehicles and water pumps have been deployed but Minns stressed they cannot be everywhere and urged everyone to use common sense.

Fourteen evacuation centres have been established in areas such as Lismore, Mullumbimby and Murwillumbah.

SES Commissioner Mike Wassing said some 20,000 people across 10,000 homes could be affected as "worst case scenario numbers".

Federal and state disaster relief funds have also been rolled out to communities in 15 local government areas in Northern NSW to help cover immediate needs such as emergency accommodation.

Workers repair damaged power lines from a fallen tree in Northern NSW. – AAP 

Lismore Mayor Steve Krieg, who was an integral figure in the recovery and reconstruction of the city after the catastrophic floods, emphasised vigilance.

"We are at the very start of this weather event," he said, as authorities warned of complacency.

"It will be quite treacherous over the coming two or three days, so please stay safe and listen to the warnings." 

Cape Byron, the easternmost point of mainland Australia, will be in the eye of the storm with dangerous storm tides and destructive winds of up to 155 km/h predicted.

Abnormally high tides and damaging surf conditions along the northern coast have also been recorded with warnings issued to avoid beaches.

Major flooding at Thora and Bellingen is possible in the coming days and on the Wilsons River near Lismore, according to the Bureau of Meteorology.

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