Severe thunderstorms passed over NSW on Thursday, dumping up to 95mm of rain in an hour, leading to 65 flood rescues.
Kanahooka High School and Para Meadows School will remain closed on Friday after they were among 21 schools in the Illawarra and Shoalhaven district impacted by the storms.
Efforts to clear debris from the Sea Cliff Bridge north of Wollongong continue after landslides blocked the famed road.
Damage from flash flooding extended through Sydney to the Hunter with the NSW State Emergency Service fielding 1337 calls for help, including 437 in the capital city.
Some 65 people needed to be rescued, including from vehicles and buildings, the SES said.
A storm over Dubbo also led to more than 200 incidents, including several flood rescues.
"Yesterday was a very busy time for the NSW SES and our partner agencies. We're asking people to check conditions before travelling," NSW SES State Duty Commander Colin Malone said on Friday.
"If you come across a flooded road, please do not take the risk. Find an alternative route."
Edmund Rice College in Wollongong was evacuated after flooding and Towradgi Public School contacted parents about midday to ask them to collect children early because of the storm.
On social media, residents posted images of floating cars caught in floodwaters metres away from a beach while others posted pictures of landslides and cracked roads.
Bellambi in Wollongong recorded 96mm of rainfall in one hour before midday, while further south Shellharbour Airport recorded 73mm.
In Sydney, Canterbury received 18mm in 23 minutes while Little Bay collected 63mm across the afternoon.
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