The final round Sunday had been delayed at the start by one hour because of rain, and then sunshine quickly gave way to hail that covered the greens in a sheet of white and led to a two-hour delay.
Mickelson will return to play the last two holes on Monday holding a three-shot lead over playing partner Paul Casey.
"So at the end of previous year, even though I played poorly, I had something happen where it seemed like overnight - it had really been in the works - where my driver speed shot up 5, 6 miles an hour, which rarely ever happens to anybody, let alone somebody in their late 40s", he said.
This was Mickelson's fifth AT&T title so it's fair to say he was a tournament specialist before this week but he was still generally a [36.0] chance and he even hit a high of [50.0] before the off. Casey, who traded at a similar price to Lefty pre-event, hit a high of [80.0] and a low of [1.5] in-play.
The 48-year-old, five-time major victor took home his second tournament in the last two years after not having won since 2013. They got pretty rough this afternoon so I totally get it.
Mickelson hit 7-iron to 8 feet on the par-3 17th and played it safe down the par-5 18th, making a 6-foot birdie for a three-shot victory.
Phil Mickelson was not happy at having to return on Tuesday to play the final two holes after bad light stopped play.
Casey was at 15 under, tied with Scott Stallings, who closed with a 66.
'Sometimes I get in my own bubble, ' Mickelson said.
Mickelson finished at 19-under 268, while Englishman Paul Casey (71) birdied the final hole for second place on 16-under.
Mickelson recorded his 44th PGA Tour victory in style with a closing seven-under-par 65 at Pebble Beach.
On Monday morning, he had a change of heart and said he thanked Casey for standing his ground.
The Portrush man turns 39 in July and while he lost his PGA Tour card a year ago and must rely in invitations to fill out his schedule, he wants desperately to be at Royal Portrush for The Open.
Mickelson's win at Pebble marks the third time in the last four years that he's finished in the top two.
I think the Vic Open's unique format - men and women playing in alternate groups on the same course and for equal prize money - is great, although I can't help thinking: why not go further? A birdie at the second was followed by eight straight pars before back-to-back bogeys at 11 and 12.