Four people have died and several were missing as major flooding in New South Wales (NSW) left about 50,000 people isolated by floodwaters.

The record rainfall, now declared a natural disaster, has been caused by a slow-moving area of low pressure and is greater than any in living memory for some residents, according to local authorities.

Heavy rains moved south overnight affecting Sydney and Newcastle, with the Bureau of Meteorology issuing weather warnings for southern parts of the state.

Australia's Prime Minister Anthony Albanese is expected to visit the flood-affected areas on Friday morning with NSW Premier Chris Minns, who earlier said the state was "far from out of the woods".

The NSW State Emergency Service (SES) said it had responded to more than 535 flood rescues in the 24 hours to 05:00 local time (19:00 GMT) - and more than 670 rescues since the flooding began.

There are more than 150 flood warnings in place with 40 of those at emergency level and authorities have re-issued earlier advice for people not to drive or enter floodwaters.

More than 100 schools have been closed because of the floods, which have left thousands of homes and businesses without power. Evacuation centres have been opened for those fleeing the flooding.

Taree, a city on the Mid North Coast, has been among the worst affected. On Wednesday, flooding at a major river in the area surpassed 6.3m (20.6ft), beating an almost century-old record for its highest level.

Authorities have confirmed the fourth death due to the floods after they recovered the body of a man in his late 70s in the early hours of Friday after it appeared he drove into floodwaters near Coffs Harbour.

Earlier, the body of a 63-year-old man was recovered on Wednesday afternoon at a property in Moto, near Taree. The fatality was later identified in an ABC News report as David Knowles. Local police have started an investigation into the incident.

Prime Minister Anthony Albanese sent his condolences to the man's family in a post in X, calling his death "devastating".

On Thursday morning, the body of a man in his 30s was found in floodwaters near Rosewood on the Mid North Coast. It followed earlier reports of a man stuck in floodwaters while driving in the area.

On Thursday afternoon, NSW police said its officers had recovered the body of a 60-year-old woman who got into trouble in her car in floodwaters at Brooklana, about 30km (18 miles) from the city of Coffs Harbour.

Police said there were a number of people missing with searches continuing for a 49-year-old man from Nymbodia who did not return home several nights ago and was last seen crossing a flooded area.

Nearly 10,000 homes are at risk of flooding in the state's Mid North Coast.

"We are bracing for more bad news," Minns told reporters at a press conference yesterday.

"It's very difficult to get supplies into some of these isolated communities," Minns said, adding that the prime minister has pledged his support for any help needed from the federal government.

Minns also urged those who are in "prepare to evacuate" areas to leave if they can, while acknowledging some won't be able to.

"They may be elderly, they might be infirm, they might have young children. But if we can get the majority of people out of harm's way, it makes everybody's job a lot easier."

Jihad Dib, NSW Minister for Emergency Services, said that the state government continued to "throw every single thing we've got" toward rescue operations.

"These aren't the records that you want to break, but we've seen more rain and more flooding in the mid and the north coast than we've ever seen before," he said.