NSW residents on standby amid a series of flood warnings and 'volatile' weather conditions

NSW braced for a tough night after several flood and evacuation warnings were issued across the state.

The "prolonged weather event", which is not expected to ease until the end of next week, has broken annual rainfall records in many locations including the Mid-North Coast where more than 350mm of water fell in the last day.

Greater Sydney's rainfall of 90mm surpassed figures recorded during last year's February floods and according to the NSW Bureau of Meteorology's (BOM) the weather situation remains "volatile, dangerous and dynamic".

"Tonight we also have the risk of rainfall reinvigorating over the Mid-North Coast, and also tomorrow," the BOM's Agata Imielska said.

"The Mid-North Coast — even though we are seeing the rainfall and rivers dropping down — we are expecting that to pick back up, so that will remain another watch point in the next 24 hours, but the rainfall itself will also shift south of Sydney, impacting the Illawarra but also the lower Blue Mountains."

As at 10:00pm, the State Emergency Service (SES) had flood evacuation warnings in place from the Clarence Nambucca region in the north of the state to the Illawarra South Coast and Southern Highlands.

The ferocity and wide coverage of the wild weather again prompted calls from the SES for people to stay safe.

"We're urging the community to be vigilant, to take this weather event very seriously," said Assistant Commissioner Dean Storey.

"It's a life-threatening weather event, monitor your local weather forecast and conditions. If you live in low-lying areas or areas that are prone to flash flooding, plan ahead and know what to do if you need to evacuate and definitely don't drive through floodwaters".

Similar calls were reiterated by NSW Premier Gladys Berejiklian earlier in the day, warning that while the storm front was moving south, NSW "was not out of the woods" and that the rain "may not stop until Thursday or Friday".

Residents in the Warragamba Dam catchment area were still on high alert overnight after Sydney's main water source reached capacity with the communities of North Richmond, Wallacia, Penrith, Sackville most at risk.

'A build-up of energy'

Chester Hill in Sydney's west took a turn for the worst after it was hit with a mini-tornado about 9:00am, bringing down trees, roofs and power lines and leaving thousands without electricity.

The wind lasted only a few seconds but damaged 30 homes and a local high school.

Resident Matthew Dinh said that he heard a big, big gust and likened it to a build-up of energy. Rahim Sherieff heard a "loud thunder".

"I thought it was lightning or something, but then when we saw in the kids' room, there were two big holes in the roof and when we came out we saw there was a lot of debris," Mr Sherieff said.

According to Ms Imielska, it is unlikely we will see this type of event again.

"That was a very localised specific event, we've always got a bit of risk of that when we are seeing severe conditions, " she said.

"We're unlikely to see something quite like that again but it's really important to be aware of it."

Near the town of Taree a house floated down the Manning River while in Port Macquarie, resident Beverley Quill had gone to work overnight and had no idea of the devastation that awaited her at home.

She was emotional as she waded through the water, retrieving family photographs and moving furniture bought for two properties she intended to rent out.

"I never thought this would happen, it's never ever happened here. It's regularly happening down the road but never here. It's just unbelievable," she said.

In more bad news for Ms Quill, who had just cancelled her flood insurance, the floodwater was expected to rise again later on Saturday evening due to the high tide.

"I was a mess before you guys were here, I've been crying all morning … I said to the kids, 'Don't leave me, I have the worst anxiety', it's really hard," she said.

Sydney's public transport network experienced multiple delays throughout the day, at Parramatta the ferry wharf was completely submerged preventing travel beyond Sydney Olympic Park.

Torrential rain also forced organisers to reschedule The Golden Slipper meeting at Rosehill after it was determined the Western Sydney track was unsafe for racing on Saturday.

Both the W-League and A-League clashes between Sydney FC and Melbourne Victory were also called off.

As of 7:00pm on Saturday, the SES said it had responded to over 6,000 requests for help and 550 direct flood rescues since Thursday. These figures were 4,000 and 500 just four hours earlier.

People requiring assistance are asked to call triple-0 if it's life-threatening or the NSW SES on 132 500 if it's about property damage help with evacuating.

The Public Information Inquiry Centre (PIIC) can also provide general information about flood-affected areas in NSW on 1800 227 228.