Prime Minister Anthony Albanese will visit flood-affected communities in NSW on Wednesday, as authorities warn other parts of the state now face flood danger.

Mr Albanese will tour areas hit hard by the flooding alongside NSW Premier Dominic Perrottet.

The visit comes a day after the PM landed back in Australia following a week-long trip to Europe for the NATO summit and to war-torn Ukraine.

It also comes as the heavy rain that has pounded areas around Sydney has shifted towards the central coast and Hunter Valley, with swollen rivers flooding communities and leaving a trail of destruction.

A flood watch has been issued for the mid-north coast on Wednesday as the weather system shifts north.

Rain was easing in Sydney and the Illawarra but the flooding remained.

SES Deputy Commissioner Ashley Sullivan said the danger for flooded communities continued and river levels would remain high for some time, prompting fears of landslips.

“This event is certainly still escalating and unfolding,” he told ABC TV on Wednesday.

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Overnight the SES received about 1200 requests for help as the Hunter region and central coast copped a drenching. Of those, 55 were calls for flood rescues as people continue to drive into rising waters.

There are 57,000 people who have been ordered to evacuate their homes, with the SES issuing 108 evacuation orders.

Twelve evacuation centres are open to support people who have been forced to flee.

On top of that, 27,000 people have been told to prepare to leave under 56 further evacuation warnings.

“We are asking them to prepare themselves, and their family and their property, in case they do need to evacuate and head to those evacuation centres or their friends and family for safe refuge,” Mr Sullivan said.

Authorities remain focused on the Hawkesbury-Nepean, where the river levels reached heights not seen for decades.

But the danger is increasing for the central coast, Hunter Valley and Mid-North Coast where there was flash flooding on Wednesday morning as river levels rose around Coffs Harbour and Taree.

“There’s still a few days to go and I suspect these flood warnings will remain in place through the weekend and in some places into early next week,” Mr Sullivan said.

The SES has 1000 volunteers supporting isolated communities by dropping supplies or helping people evacuate. Their efforts are backed up by an additional 100 ADF personnel who will arrive on Wednesday, alongside emergency workers from interstate.

Mr Albanese said the Commonwealth was working with the state government to provide assistance requested during the crisis.

“People want governments to work together in the interests of the population not to engage in politics,” he told ABC News on Wednesday.

“We want to make sure that the support is available as soon as possible, that’s why we’re being very quick to act in partnership with the NSW government and it is pleasing that we’ve been able to work together so strongly.”

The federal government has already assisted with ADF deployment and joint disaster payments with the state government to 23 local government areas.

Emergency Management Minister Murray Watt said the Commonwealth was considering whether further disaster recovery payments would also be extended to flood victims.

Rain over Sydney had eased by Wednesday but roads remain cut off, debris is floating in floodwaters and businesses are completely submerged.

Some properties have been isolated for days and infrastructure such as roads, power, water, and telecommunications are damaged. Power has been cut to thousands of residents.

River levels have continued to rise, with the Hawkesbury at North Richmond reaching more than 14 metres.

There is still major flooding at North Richmond, Windsor, Sackville, Lower Portland and Wisemans Ferry, with more rain expected.

Heavy rainfall since Sunday morning has caused dramatic water-level rises across the Hunter River catchment.

The Bureau of Meteorology said there was minor to major flooding at Wollombi Brook and the Lower Hunter River at Bulga, Wollombi, Maitland and Singleton.

Overnight, people in the Hunter community of Broke were cut off by rising floodwaters.

-with AAP