A third person from Lismore has died in the NSW flood crisis engulfing northern NSW as Greater Sydney braces for a deluge.

“We’ve recovered a third body this morning,” NSW Deputy Premier Paul Toole told reporters on Wednesday.

“That was a male in the CBD of Lismore. That now takes our total deaths to four. 

“This is terrible … one life lost is too many.”

The latest fatality comes after the body of a woman in her 80s was found inside a South Lismore house on Tuesday afternoon. She was the second elderly woman to die after being trapped in a flooded home in the area.

Another man who disappeared in floodwaters in Lismore on Sunday is presumed dead, while a man died on the Central Coast on Friday.

“No-one would have predicted we were going to see a 14.4m rainfall event or flooding in that area,” Mr Toole said.

Greater Sydney is also bracing for potential “life-threatening” flash flooding. 

The torrential rain forecast for Sydney and surrounding areas – as much as 200mm – will hit late on Wednesday and early Thursday, the Bureau of Meteorology said.

“In the Sydney area we have minor to major flood warnings current for the Hawkesbury-Nepean and we could see minor flooding develop as far eastward as the Penrith area which will continue to develop as the rain continues to fall,” the BOM’s Dean Narramore said on Wednesday.

The heavy rainfall will also affect Newcastle, the Blue Mountains and Wollongong.

NSW SES is advising residents within parts of Chipping Norton in southwest Sydney to evacuate in the next few hours.

“We still have a large number of helicopters up north that are helping … around the Ballina area particularly. And we have troops on the ground as well to help,” said SES Commissioner Carlene York. 

“We are actively door knocking.”

Warragamba Dam is overflowing, with Water NSW warning it may continue for up to two weeks, threatening thousands of homes in the Hawkesbury and Nepean area.

The SES received more than 2200 calls for help overnight on Tuesday and undertook 300 flood rescues in the northern area of the state which has been inundated with record floods centred on Lismore.

The Red Cross on Wednesday confirmed to AAP that 894 enquiries had been made in NSW alone by family members looking for their loved ones, with 25 matches secured.

Meanwhile, federal Services Minister Linda Reynolds said 90,000 claims for disaster relief payments were submitted on Tuesday.

There are several flood warnings for the Greater Sydney area, including the Upper Nepean at Menangle, the Hawkesbury River at Richmond and Windsor, the Colo River at Upper Colo and the Georges River.

The communities in the path of the floods are the same ones devastated by floods just a year ago.

Thousands of people spent the night frantically sandbagging their homes and businesses.

People in low-lying areas around Windsor and Pitt Town, northwest of Sydney, have also been told to prepare to evacuate.

The slow-moving weather system arrived in Sydney late on Tuesday, dumping rain over parts of the Hunter and Metropolitan, Illawarra, South Coast and parts of Central Tablelands and Southern Tablelands.

Meanwhile, Emergency Services Minister Steph Cooke says it’s too early to know exactly how many homes in western Sydney could be impacted by the overflowing Warragamba Dam.

“We know there’s 130,000 residents in and around that area. It depends on exactly where the rain drops and how much it drops, so we are on high alert,” she told the Seven Network.

While the rain has eased in the Northern Rivers region, the crisis is ongoing with some 35,000 people ordered to evacuate.

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