A man is lucky to be alive after falling into a six and a half metre deep drain during a monster storm that caused havoc across Sydney, triggering flood rescues and hundreds of calls for help.

The dramatic rescue at Balmoral in Sydney’s North Shore saw two strangers, Danilo Dimas and Angus Finlayson, jump into the uncovered drain to save the man’s life.

Dimas, an ex-Brazilian policeman working at a nearby bar, had only moved to Australia three weeks ago.

“I saw just his face in the water and I just, I don’t think and I jumped. And when I jumped, I realised that it’s too deep,” Dimas said.

Finlayson described the harrowing rescue: “I couldn’t see anything in the blackness and Danilo just jumped straight in and held the guy up and then we pulled him out.”

The elderly victim was taken to hospital with minor injuries.

The man fell into a drain during the storm.The man fell into a drain during the storm. Credit: 7NEWS

The storm caused widespread chaos across Sydney, with jet skis seen on the streets of Fairfield as a nearby creek flash flooded.

A local windscreen fitter rescued neighbours as rivers poured through backyards, ruining carpets, furniture and walls.

“Very, very scary. I was crying inside,” said Merry Shiba, one of 42 priority rescues.

Authorities responded to almost 500 calls for help.

“This is the worst it’s ever been. Like two hours, there was no warning,” one resident said.

A jet ski on the streets of Fairfield.A jet ski on the streets of Fairfield. Credit: 7NEWS

At Canley Vale, the flood came in waves as desperate drivers made their way past the Bunnings near Bankstown Airport.

Milperra Road became a boating hazard, while on Parramatta Road, pedestrians were forced to walk through water as traffic was swamped across the city.

Residents say it’s the worst flooding they’ve seen in 60 years.

“You’ve got the council and all that. They turn around and say it won’t flood, won’t flood. Floods every year,” one frustrated resident said.

Authorities responded to 500 call for help.Authorities responded to 500 call for help. Credit: 7NEWS

The fierce weather took many by surprise, with the rainfall coming very hard and fast without as much warning as authorities would have liked.

“The rainfall came very hard and fast and there wasn’t as much warning as they would have liked,” Bureau of Meteorology’s Jonathan How said.