The rain has eased in New South Wales but flooding continues and a new threat has emerged with damaging winds threatening to topple trees and down powerlines.
The Bureau of Meteorology says gusts in excess of 90km/h are expected for the Mid-North Coast, Central Coast, Hunter, Sydney, Illawarra and South Coast regions on Wednesday.
The torrential rain that has battered the east coast for more than a week has eased, but flooding continues and there are more than 60 evacuation orders across NSW.
The NSW State Emergency Service received nearly 3000 calls for help in the past 24 hours.
The east coast low that brought the rain is now off the Illawarra coast and moving south.
Sydney Trains is warning the severe weather is causing significant disruption and delays and is advising commuters to avoid non-essential travel.
There's major flooding along the Hawkesbury River in western Sydney at North Richmond, Windsor, Sackville, Lower Portland and Wisemans Ferry.
SES Assistant Commissioner Sean Kearns says the river is still rising with a peak of 14.3 metres expected at noon.
"They are saying it could get as high if not higher than what people experienced in March last year," he told Sydney radio 2GB on Wednesday.
Along the Upper Nepean at Wallacia river levels fell below the major flood level of 11 metres early on Wednesday with moderate flooding at Menangle, Camden and Wallacia.
Around 40,000 people in NSW are under evacuation orders, including in dozens of suburbs around Greater Sydney, after unrelenting torrential rain on Tuesday.
Sydney's northern beaches copped the worst of the downpour with about 2000 people in low-lying areas near Manly Dam in Sydney's north warned to prepare to evacuate as the dam began spilling on Tuesday.
People were living in the vicinity of Narrabeen Lagoon were ordered to evacuate by 7pm and warned they could be trapped without power.
About 4500 homes and businesses lost power in Shoalhaven, the Illawarra and Southern Highlands on Tuesday afternoon as storms downed trees and powerlines.
Endeavour Energy said about 1700 homes and businesses near flooding rivers in western Sydney were also without power on Tuesday night, and a further 300 were expected to lose power overnight.
Many rivers are likely to continue flooding until peaks subside.
The SES said major flooding was happening along the Colo River and In the Hunter region, Bulga southwest of Singleton could see worse floods than last year on Wednesday morning, with major flooding likely to reach Singleton as well.
The death toll from flooding in NSW in recent weeks increased to eight on Tuesday with the discovery of two bodies, near where a car had previously been found in a stormwater canal at Wentworthville in Sydney's west.
In the Northern Rivers, a fifth flood-recovery centre is set to open on Wednesday at Casino, joining others already operating at Mullumbimby, Murwillumbah, Kyogle and Lismore.
Deputy Premier Paul Toole said the centres will house numerous government agencies to help support flood victims.
Australian Defence Force members will also be stationed at the centres, and 1300 personnel were due in the Northern Rivers by the end of the day on Tuesday.
Prime Minister Scott Morrison and Premier Dominic Perrottet will visit the region on Wednesday.
NSW small businesses and not-for-profits affected by the floods can now apply for up to $50,000 in government support to cover the cost of clean-up and repairs or to restock and reopen.
Mr Perrottet said the Flood Disaster Recovery Small Business Grants would provide a much-needed lifeline to small businesses hard hit by flooding.
