NSW Premier Chris Minns is in the state's north ahead of the cyclone's expected landfall, which has prompted warnings for residents in several areas including parts of Lismore and Kyogle to evacuate by 9pm on Thursday.
The category two cyclone is expected to lash northern NSW and southeast Queensland with heavy rain and wind, forecast to peak late on Friday and early Saturday.
Essential Energy has advised that 10,000 homes and businesses are without power due to heavy winds, and may remain disconnected for long periods of time as the dangerous weather hinders the ability of crews to survey or repair the damage.
Lismore Soup Kitchen chaplain Ian Phillips told AAP there had been a calm before the storm.
But the conditions threaten to change soon.
"People are anxious about what might happen," Mr Phillips said.
"We're just gearing up for them to have a safe place to camp for as long as they need to ... there's a lot brewing for them because of their previous experience."
An evacuation centre has been set up at Southern Cross University, where people sheltered after the devastating 2022 floods.
"People we know that are sleeping rough, they've headed there already, and some will this afternoon," Mr Phillips said.
Acting SES chief superintendent Stuart Fisher said the cyclone could be worse than the 2022 floods.
Up to 700mm of rain could fall on the region with authorities advising residents "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 Mr Minns stressed they cannot be everywhere and urged common sense.
"(Cyclone) Alfred is behaving like a completely unwanted house guest," the premier said in Lismore.
"It's going to be late, but linger, and unfortunately that means the window for destruction in our community - heavy rains, winds, powerful surf - is longer than we would have otherwise liked."
Fifteen evacuation centres have been established around the northern rivers region and more than 300,000 sandbags have been distributed.
SES Commissioner Mike Wassing said 20,000 people across 10,000 homes could be affected as "worst-case scenario numbers".
Federal and state disaster relief funds have been rolled out to communities in 15 local government areas in northern NSW, and on Lord Howe Island, to help cover immediate needs such as emergency accommodation.
Emergency Management Minister Jenny McAllister advised people to listen to warnings, prepare their homes and check-in on friends and neighbours.
"If we all do these things, if government prepares, if community prepares, we can get through this," she said.
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. It will be quite treacherous over the coming two or three days, so please stay safe and listen to the warnings," he said.
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.
Intense rain could push rapid and dangerous river rises, the Bureau of Meteorology warned, with potentially major flooding along the Tweed, Wilsons, Bellinger, Brunswick, Nambucca, Richmond, Clarence, Orara, Macleay, Hastings and Camden Haven rivers.
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