State Emergency Service spokesman 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.
"We've seen about 65 flood rescues in the last 12 hours alone so our crews are still keeping very busy," he told the Seven Network on Thursday.
"We still have that flooding in the Hawkesbury Nepean valleys, so we've got a big focus on that," he said.
More than 6000 Hunter residents have fled to higher ground as rising water levels threaten 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 also evacuation orders for several Hunter Valley towns in place, 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.
With rain easing in Sydney the clean-up and assessment of significant damage has begun.
The SES issued 57 return-with-caution alerts overnight to residents in Lansvale, Moorebank and Chipping Norton in the city's southwest.
Prime Minister Antony Albanese has announced disaster recovery payments of $1000 for eligible adults and $400 for children. Applications for the support will open at 2pm on Thursday.
Mr Albanese and NSW Premier Dominic Perrottet on Wednesday visited deluged parts of the Hawkesbury, a region that has endured four floods in the past 18 months.
