A trough and cold front is moving across the state on Friday, bringing further widespread rain to the eastern half of NSW including the western slopes and ranges, central NSW and the south coast.
Up to 100mm of rain could fall at motorsport mecca Mount Panorama over the weekend, potentially leading to flooding along the Macquarie River in Bathurst.
Severe thunderstorms could also bring damaging winds to the region.
Free sandbags will be available in Bathurst while volunteers are checking in with residents and tourists camping near the Macquarie River.
Saturday is set to be a high-risk day for Sydney, with warnings of renewed river flooding to the city's west months after record peaks were observed.
The SES has warned people near Penrith to stay informed about predicted river rises in the Nepean, Hawkesbury and their tributaries.
"We're very conscious your communities have experienced four floods within an 18-month period and acknowledge the anxiety you will be feeling at this time," Emergency Services Minister Steph Cooke said on Friday.
Conditions will ease briefly on Saturday morning before a low-pressure system forms along the coast in the afternoon, bringing renewed rain in the evening.
The worst of the weather should ease by Sunday, according to the Bureau of Meteorology.
Statewide, the SES received 365 calls for assistance in the 24 hours to Friday morning, including four for flood rescues.
Cotton town Warren, where waters have been above the major flood level since Monday, is subject to one of 14 watch-and-act flood alerts in NSW.
Renewed and prolonged flooding is continuing in inland NSW at the Namoi, Macquarie, Bogan, Lachlan, Murrumbidgee, Murray, Edward, Culgoa, Birrie, Bokhara, Warrego, Paroo, Barwon and Darling rivers.
Inland towns being monitored closely include Gunnedah, Narrabri, Tamworth, Dubbo and Forbes.
Emergency services don't want people entering flooded causeways and other river crossings, police said.
"It wasn't very long ago we had a five-year-old boy ... who was killed in a car that was washed off a bridge," NSW Police superintendent Bob Noble said, referring to an incident in Tullamore two weeks ago.
"You can imagine how devastating that is for that family. It's a terribly hard way to learn a lesson for society."
More than 90mm fell at Sydney's Observatory Hill on Thursday, helping topple the city's annual rainfall record set in 1950.
Farmers are also concerned the latest deluge will destroy crops while graziers have been warned to shelter lambs and sheep.
The bureau has warned livestock is at risk with temperatures set to plunge in the Illawarra, south coast, southern tablelands, southwest slopes, Snowy Mountains and ACT regions.
14°C