The cyclone has begun to impact southeast Queensland and northern NSW as the category two system approaches the Australian coast despite stalling again overnight.
Tens of thousands of homes are without power after wind gusts destroyed trees while heavy rain has triggered flooding, forcing people to flee their homes.
"It is slowly continuing towards the coast. Overnight we saw it packed a punch," Queensland Premier David Crisafulli told ABC News.
The wild weather will only get worse, with Alfred set to cross the coast near Brisbane between Noosa and Beenleigh on Saturday likely as a category two storm.
"What we need to do is to hope for the best, but prepare for the worst. We absolutely need to prepare for the worst," Prime Minister Anthony Albanese told reporters on Friday.
Alfred was initially set to arrive on Thursday night but stalled in recent days, adding extra anxiety to millions of people counting down to the first cyclone to hit the southeast since 1974.
"We should not think that slower means better," Mr Albanese said of Alfred's meandering approach.
"As it is over warmer waters (it has) the potential to increase the intensity of it."
Alfred slowed down again overnight but its impacts have begun to be felt with damaging wind gusts across southeast Queensland and northern NSW.
NSW's Cape Byron has copped winds up to 120km/h while Gold Coast airport recorded 100km/h gusts.
Heavy rain has lashed communities and triggered flooding, with 48-hour totals of more than 400mm recorded in northern NSW and up to 250mm in Queensland's southeast.
"Unfortunately the northern river systems of NSW are already on their way to major flooding," the Bureau of Meteorology's Sarah Scully said.
Schools, businesses, supermarkets and airports have been closed with people not in high risk areas told to stay home as Alfred made its presence felt.
More than 40,000 homes were without power in Queensland on Friday along and another 35,000 in northern NSW due largely to flying debris, with an elderly woman in Mudgeeraba treated after a tree smashed into her home.
"We continue to urge the community to plan for power outages lasting a week or more," an Energex spokesperson said.
Thousands of people spent their first night in refuge centres across the region after being forced to evacuate with more expected to be asked to flee on Friday.
Northern NSW's low lying areas are set to be inundated, prompting more than 100 army personnel to fly in and assist more than 2000 SES personnel.
"I wouldn't wish this on my worst enemy. This is incredibly traumatic for a community who has gone through so much," NSW Premier Chris Minns told ABC North Coast Breakfast.
More than one million sandbags have been distributed to Queensland alone in the anxious countdown to Alfred.
"We're nervous about what damage is going to be caused but no one knows," Charmaine Harris told AAP outside her sandbagged Brisbane home.
But Alfred couldn't come soon enough for some.
""We've cleared the house up and the yard, gotten food and now just sick of waiting," Kylie Madge told AAP at the Brisbane coastal community of Wynnum on Friday.
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