Flooding threat as rain drenches eastern Australia

Suburbs on Sydney's fringes are facing the threat of significant flooding as intense storms slowly shift south.

More than a month's worth of rain fell over Sydney, Port Macquarie and Taree on Friday, delaying trains, cutting power and leading to evacuation alerts.

The New South Wales State Emergency Service was involved in 44 flood rescues by Saturday morning and had received more than 4000 calls in the past 24 hours.

The Cooks River burst its banks at Earlwood after 7am on Saturday, triggering road closures and early morning traffic.

Moderate flooding has also taken place at North Richmond and Windsor in Sydney's northwest.

The Bureau of Meteorology's Helen Reid said many parts of the region had been hit with more of 100mm of rain in the past 24 hours.

"As a result of the rain, many rivers have risen with minor flood warnings being issued overnight," she said on Saturday.

"Since yesterday, the heaviest rainfall has been at Darkes Forest with a total of 228mm there, and it's still raining."

The focus of the rain is expected to be in northeastern and southeastern NSW and more 33 flood warnings remain across the state.

But Ms Reid said there could be reprieve on the horizon for some Sydneysiders.

"We are expecting a clearance of rainfall for Sydney today," she said.

"A lot of areas have already seen the heaviest rainband move through, though we are looking at it being an easier day in Sydney as we look towards what water has fallen."

The severe weather risk was expected to have moved south of the capital on Saturday morning.

But the bureau warned isolated severe thunderstorms may redevelop on Saturday afternoon.

Up to 150mm remained possible within a six-hour period for areas stretching from the Blue Mountains hundreds of kilometres to Narooma.

Evacuation orders were issued by the SES for several locations including along the Hawkesbury Nepean and for low-lying parts of Chipping Norton in the heart of western Sydney.

Numerous rivers - including the Hawkesbury, Nepean, Georges, Lower Hunter, Myall, Macquarie and Woronora - were on flood watch.

"With the forecast rainfall, further river level rises and moderate to major flooding is possible from Saturday morning along the Hawkesbury and Nepean Rivers," the Bureau of Meteorology warned on Friday evening.

Liverpool and Milperra in southern Sydney could experience moderate flooding from the Georges River from Saturday morning.

Surfers and other beachgoers were also warned to stay "well away from the surf and surf-exposed areas" due to dangerous conditions, particularly at east-facing beaches.

Scores of community sport teams had their winter seasons delayed with flooded grounds from Wollondilly to the Northern Beaches closed all weekend.

Relief won't be in sight for Nepean and Hawkesbury communities downstream of Warragamba Dam.

The reservoir holding most of Sydney's water supply is expected to spill from Monday.

Premier Chris Minns advised residents to remain alert and up-to-date with warnings in their local areas.

"It is a volatile event and we need to make sure that we've got the latest information ... but it does require everybody being alert," he said on Friday.