A storm that dumped more than 300 millimetres of overnight rain on NSW South Coast towns has continued to track past Sydney into Thursday night, prompting dozens of flood rescues.
The Bureau of Meteorology indicated Greenwell Point in the Shoalhaven received 368mm of rain since 9:00am Wednesday, including 177mm in one hour.
Bellambi in Wollongong's north received 116mm since 9:00am on Thursday with 96mm falling in one hour.
The bureau issued several warnings for "very dangerous thunderstorms" for parts of Sydney throughout the afternoon, and for the Central Coast past Wyong in the evening.
The system hit Wollongong and Shellharbour at about lunchtime and caused chaos with roads and school closures and over 600 calls to the State Emergency Service for assistance.
The SES said it has carried out 31 flood rescues across the Illawarra and Greater Sydney regions.
"There were a number of flood rescues in Unanderra where people drove into flooded water," Sharon Fox from the SES said.
Earlier, a number of Illawarra schools were forced to close early, including Kanahooka High School and Albion Park High, with Woonona High School students evacuated.
"There were a couple of occasions where schools needed assistance with getting children out," Ms Fox said.
"They weren't necessarily life-threatening but there was certainly a large amount of water that inundated some of the school areas."
In the southern Sydney suburb of Miranda, several cars were inundated after heavy rain caused flash flooding in a matter of minutes.
Bystanders said some drivers were forced to escape from their vehicles and find higher ground.
"My car, which was parked here — and I don't usually park it here — it's going to be a write-off," James Martin said.
"That's hard … especially because I don't have insurance."
Airport, road, rail delays
Passengers flying in and out of Sydney airport should expect delays after the day of wild weather.
A Sydney Airport spokesperson said some services were experiencing diversions due to the storm activity, and travellers should check with their airline regarding the status of their flight.
The Seacliff Bridge at Coalcliff is closed due to rock falls, and flooding at the Audley Weir in the Royal National Park has closed the road in both directions.
The Princes Highway has reopened at Waterfall after being closed due to flooding, however, South Coast trains are still not running between Waterfall and Kiama.
Nursing home inundated
Acting SES zone commander Tom Jory said overnight call-outs were mainly at Greenwell Point and Culburra Beach.
"One of those jobs is a nursing home where we are working with the RFS," he said.
"We have been out there a couple of times overnight to try and solve some localised flooding that they are having."
The greenkeeper of the Greenwell Point Bowling Club in the Shoalhaven, Craig Lurton, said he tipped 251mm out of the gauge this morning.
"[The greens] are underwater — we're going to need flippers today," he said.
"I live in Nowra, so I was unaware of it — we only had a couple of millimetres in there."
