State Emergency Service Deputy Commissioner Ashley Sullivan says the SES received around 1200 requests for help in the last 24 hours, with about 900 of them in the Central Coast, Hunter and the Mid-North Coast regions where the situation is evolving.

"We've seen 65 flood rescues overnight, so certainly a busy time for our crews," he told ABC TV on Thursday.

There are 74 evacuation orders covering about 43,000 people, alongside 36 warnings to be ready to leave covering about 17,000 people.

With rain easing in Sydney the clean-up and assessment of significant damage has begun.

The SES has issued 58 return-with-caution advices, giving the go-ahead to about 35,000 people to go back to homes where the flood threat has eased, mostly in Sydney's southwest.

The Hawkesbury-Nepean and the Georges and Woronora catchments and rivers are still in crisis mode, with flood warnings remaining and debris, contaminants from spilled chemicals and fallen power lines posing risks.

"We're supporting community's return to their home, particularly around the Georges and Woronora where we've seen floodwaters recede," Mr Sullivan said

Fire service personnel will begin to move into those areas to help communities with hosing out and removing debris from their homes.

"So we're in a mixed response at the moment of returning communities to their homes, but still responding to the evolving threat up in the Mid-North Coast and Hunter and Central Coast," Mr Sullivan said.

More than 6000 Hunter residents have fled to higher ground as rising water levels threatens their homes, while the New England Highway remains closed at Singleton and Maitland .

An evacuation order has been issued for Singleton, which is experiencing major flooding.

There is moderate flooding at Wollombi and Maitland after the Hunter River peaked at 13.7 metres overnight, exceeding the 13.15m level of the March floods.

Electricity provider Ausgrid is warning the town's residents could be cut off as it battles to restore power to approximately 3000 customers in parts of the Central Coast, Lake Macquarie and pockets of Sydney.

There are evacuation orders in place for several Hunter Valley towns, including Bulga, Broke, Wollombi and Dunolly.

Meanwhile, the Bureau of Meteorology has cancelled the severe weather warning for the Mid-North Coast as the low-pressure system moves out to sea, with showers expected to ease.

Applications for support payments of $1000 for eligible adults and $400 for children will open at 2pm on Thursday.

Mr Albanese and Premier Dominic Perrottet on Wednesday visited deluged parts of the Hawkesbury, a region that has endured four floods in the past 18 months.

Australian Associated Press