The NSW State Emergency Service (SES) has been dispatched to nearly 630 incidents across the state in the last 24 hours, including 10 flood rescues.
There are 42 warnings in place for residents across the impacted areas from Wollongong to Goondiwindi.
Residents at Gunnedah have also been warned to prepare to isolate.
The Bureau of Meteorology is keeping a close watch on the Namoi River which could reach major flood levels on Saturday.
"There's a lot of water moving through that system and that is the most significant flood warning we have," the bureau's Christie Johnson said.
Minor flooding could occur in north Richmond and Windsor in far western Sydney on Friday.
Rain slowed across the northern and central western slopes as well as inland overnight.
There will be a drop off in coastal areas before easing on Friday and extending into Saturday and Sunday.
"The weather system that's been bringing all this heavy rainfall has now moved off the east coast," Ms Johnson said.
"We're expecting rainfall totals to be much lower for the remainder of today between five and 20mm."
But she noted there are still some showers for Sydney, the Hunter region and the mid north coast of the state.
Ms Johnson said the weekend is expected to have "much more settled" weather but there are potential light showers along the NSW coast.
More than 356mm of rain has fallen in three weeks in Sydney's CBD, closing in on the city's all-time August record of 482mm, set in 1998.
Police divers recovered the bodies of a father and son in floodwaters on Thursday while a third man escaped to safety after the flash deluge caused dangerous conditions.
Their car had crashed into a tree and went into the Macdonald River at St Albans, northwest of Sydney, late on Wednesday.
The pair are yet to be formally identified but are believed to be aged in their 20s and 50s.
A 24-year-old man survived after escaping the car and reaching the riverbank.
15°C