Sydney copped buckets of rain that included a 100mm deluge in three hours overnight into Friday, sparking flash flooding and 42 rescues.
Emergency services said a dozen properties were evacuated in Fairfield, in western Sydney, due to floodwater inundating homes.
Six people needed to be rescued from a park in the same suburb after they were stranded due to flash flooding.
A sinkhole opened up in the Sydney CBD on Friday morning after rain pounded the city, with workers still repairing the damage at 2pm.
It was believed to have been caused by a burst water pipe.
Images had earlier shown a grocery delivery truck had become stuck in the hole before assistance vehicles towed it out.
The nearby St Mary's Cathedral College sent its high school students home on Friday morning, with water supply to the area cut off.
More than 300 emergency service workers and volunteers across the city responded to more than 560 incidents, particularly in the southwest, NSW State Emergency Service said.
Most requests involved flood rescues, inundated properties, leaking roofs and fallen trees.
"When you're getting 50 to 60 millimetres an hour, that will cause the water to rise rapidly, which means people were just getting caught out," SES Assistant Commissioner Sean Kearns told the ABC.
The SES said people should be vigilant during a sudden weather event such as this.
"Flash flooding is a real risk and can occur quickly, without much warning," Assistant Commissioner Dean Storey said.
"We urge people to steer clear of floodwaters and never drive through a flooded road - regardless of how safe you think it may be."
Thousands of commuters were stranded on major arterial roads, including Anzac Bridge, and parts of Parramatta Road were closed.Â
But tens of thousands of revellers preparing to celebrate the annual Mardi Gras parade can breathe easy.
No more than a shower or two is possible for Saturday night's march through the city centre while temperatures will be in the low 20s.
Other parts of Australia have also been deluged.
The remote town of Birdsville in southwest Queensland received nearly 60 per cent of its annual rainfall of 161mm in one day after 93mm of rain fell.
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