Not even Mother Nature can stop Jamie Whincup from winning.

The soon-to-be six-time V8 Supercar champion scored back-to-back victories on a day of extremes at the season-ending Sydney 500 on Saturday.

Whincup opened the weekend with a win in hot and humid conditions, before doubling up in a rain-shortened second race hours later.

A severe storm battered Sydney Olympic Park midway through the evening sprint, flooding parts of the street circuit and forcing a temporary suspension.

“It was pretty loose out there,” said Whincup.

“There were big rivers across the track.”

The Red Bull Racing star was leading when the red flags were waived after a flawless start, and maintained his place when racing resumed for three laps behind a safety car.

“I was thinking they were going to try to do a one-lap dash at the end – that would’ve been carnage,” Whincup added.

“There’s not enough dollars up pit lane to be tearing cars up.”

Time restrictions meant the race wasn’t completed, but full championship points were still awarded.

Not that it matters to Whincup, who secured the 2014 title – a record sixth in seven years – last round but will have to wait till Sunday to be officially crowned.

Holden’s Shane van Gisbergen finished second, with Volvo sensation Scott McLaughlin in third.

It was a different picture earlier in the afternoon, when Whincup notched up his 88th career win – and lucky 13th of the year.

The Red Bull Racing driver started from second on the grid, but got the jump on Erebus Motorsport’s maiden polesitter Will Davison.

Whincup was quick to capitalise on his flawless start, sprinting out to a 2.5sec lead by lap four but lost it to Holden’s Tim Slade after a safety car intervention.

He regained his place with just 10 laps to go, with Slade finishing second and Ford’s David Reynolds third.

“I like to think I’ve raced today the same I have all year – and that’s to try and make educated moves and push as hard as I can but keep it safe and bring it home,” Whincup said.

There was no smile on the face of Whincup’s teammate Craig Lowndes – only a grimace of pain after a heavy shunt into a concrete barrier during qualifying.

The team managed to get the car back for the two races, but the crash left Lowndes with suspected cracked ribs. He finished 13th and 20th.

Returning star Marcos Ambrose, who crashed in qualifying just moments before Lowndes at the same corner, finished 20th and 21st in his first two races back in the series after nine years in America’s NASCAR.

The two-time champion is steering a wildcard entry for Dick Johnson Racing this weekend ahead of his full-time drive with the to-be-formed DJR Team Penske.

Qualifying for Sunday’s longer 250km race begins at 11.05am (AEDT).