Hundreds of people have been rescued during one-in-500-year flooding after parts of Australia’s east copped four months of rain in two days.

Flooded residents are warned to prepare for long periods of isolation while others are urged to evacuate.

WATCH THE VIDEO ABOVE: Historic floods devastate Hunter and Mid North Coast of NSW.

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Almost 300 flood rescues were carried out on Wednesday, including helicopters lifting stranded occupants off their roofs to safety in the Hunter and Mid North Coast regions of NSW.

More helicopters and crews are on their way to join the rescue efforts.

The state and federal governments have activated disaster support — including emergency accommodation — for 16 local government areas and the Insurance Council of Australia (ICA) has declared it a “significant event” and started collecting data for claims.

“These floods and severe weather are having a huge impact on communities across the Hunter and Mid North Coast, which is why we’re working with the Minns Government to activate this support,” Federal Emergency Management Minister Kristy McBain said.

“From emergency accommodation, to support for small businesses and councils to repair damages — we’re ensuring support is available during this event and as communities turn their focus to recovery.

“These conditions are expected to continue into the week, so it’s really important that people are aware of the flood risk in their area by keeping up to date with the warnings and that they listen to the advice of emergency services.”

Record-breaking floods in Taree came from a staggering 412mm of rain in two days, as the Manning River peaked at 6.4m and inundated businesses across the town.

“(That) is essentially five times the monthly rainfall for May for Taree,” the Bureau of Meteorology’s Steve Bernasconi said.

“In essence, it’s received one-third of its average annual rainfall in two days.”

Natural Hazards Research Australia chief executive Andrew Gissing said flooding in the town was unprecedented, surpassing a 1929 record.

“The average frequency of the Manning River reaching peak flood level at Taree is once every 500 years,” he said.

A coastal trough is moving slowly over the NSW Mid North coast, with some parts expected to be hammered with another 200mm of rain in coming days.

More than 1600 SES volunteers are on the job as locals band together to support their communities.

Taree might only be isolated for a day, but other parts of the state could be trapped for up to a week, SES Commissioner Mike Wassing said.

“We’ve been engaging with these communities well prior to these floods arriving, we’ve had the evacuation orders out, and now today (are) very much our focus for the rescue operations,” he said.

More than 100 warnings were in place on Wednesday afternoon with 48,000 people isolated by floodwaters after falls of up to 280mm in some areas.

“For those people waiting to be rescued, we know this takes time,” Emergency Services Minister Jihad Dib said.

“We are working on it. It is a priority and we ask you to be patient.

“We have seen images of people on roofs. You are the absolute priority.”

The bulk of rescues were in Taree, Wingham and Glenthorne, including several cars caught driving into floodwater.

Many people reported water rising into their homes, with some seeking refuge on their roofs, the SES said.

Gripping video showed Glenthorne woman Holly Pillotto being rescued by a NSW Police Rescue helicopter.

She had an agonising wait alongside her roommates Sam and Jordan Halloran and their young son, before they were winched to safety.

“Can’t thank everyone enough for your kind words and efforts to help us,” Jordan said.

“Huge thanks to the NSW Police Rescue and the SES for getting us out safely.

“Now we wait to go home eventually and assess our losses and start over.”

Wingham Plaza is currently under a foot of water, a video posted on social media by the shopping centre’s butcher showed .

Aerial pictures shared to the town Facebook page noticeboard had painted a grim picture.

“We are keeping a close eye on the evolving situation in New South Wales, and most of our stores remain open with plenty of food and supplies,” a Coles spokesperson told 7NEWS.com.au.

“Our Wingham and Kempsey stores have had to unfortunately close at this stage, and we will reopen these as soon as it is safe to do so.

“Our teams are working hard to ensure we have extra food deliveries on their way to our stores, so our communities can rest assured that we will continue to serve them as long as it’s safe to do so.”

Cattle have been pictured on Old Bar Beach after reportedly being washed down Manning River.

“They are washing out of the Farquhar Inlet, down the Manning River, which leads out to the ocean,” Ingenia Holiday Parks Old Bar Beach visitor David O’Halloran told the ABC.

“Several locals are around, trying to catch the others in the public park area.”

Another 200mm to 300mm may fall in the next two days, hitting Coffs Coast and northern tablelands.

Some northern catchments are already saturated after Cyclone Alfred in March.

A stay-indoors message was issued for elevated inland parts of the Mid North coast, including Bowraville and the outskirts of Coffs Harbour.

A significant event declaration is in place but the ICA said that may be escalated to an “insurance catastrophe” given the scale of the flooding.

“The unfolding weather situation along the New South Wales Mid North Coast and Hunter regions is already breaking records, with evacuation orders in place for many towns and more rain forecast for the coming days,” said ICA chief executive Andrew Hall.

“While this significant event declaration is for those regions most impacted by flooding to date, we are closely monitoring the severe weather across the entire state.

“Insurers acknowledge these regions also experienced significant flooding in 2022.

“This flooding event is an ongoing emergency so while it’s important people lodge a claim with their insurer as soon as they can, safety is our number one priority.

“We urge residents in these areas to remain alert and listen to the advice of local emergency services.”

‘My houseboat went’

For Ray, a cleaner at Bulahdelah’s Plough Inn Hotel, the rising river has already caused damage.

“My houseboat went,” he told AAP.

“I was looking across the jetty (Tuesday) morning and it wasn’t there.

“It’s the icing on the cake, (the weather) has been on and off for the last couple of weeks.”