The rain forced the start to be delayed more than an hour Sunday and the hailstorm prompted a delay of over two hours.
Mickelson had a three-shot lead over Paul Casey with two holes to play when it was too dark too finish Sunday night because of delays from rain and a hail storm.
We'll get to some nuggets backing each argument, but let's first hear from the guy whose opinion matters most in all things Mickelson - the ubiquitous lefty himself. I have good vision, I can see fine and I wanted to continue.
Casey resumed with a three-foot par putt at the 16th hole on Monday, while Mickelson had already completed the hole.
Even so, it was the fourth time Casey took a 54-hole lead of at least two shots into the final round on the PGA Tour and failed to win. "I've got two hard holes coming up".
Phil Mickelson has downplayed suggestions that his win at Pebble Beach on Monday will have any bearing on his chances of completing the career grand slam when the U.S. Open is contested at the same venue in June.
"Sometimes I get in my own bubble", Mickelson said.
"To be part of the lore of Pebble Beach, the history of Pebble Beach, I walk around here pinching myself", he said.
His brilliant play still shared the stage with weather that was freakish even by Pebble standards.
Instead, he had to return early Monday morning to complete his 44th PGA Tour victory, claiming a fifth AT&T Pebble Beach National Pro-Am while also becoming the eighth-oldest victor in PGA Tour history.
Mickelson and Casey were unable to tee off on the par-3 17th due to darkness and will return on Monday morning.
Mickelson finished at 19-under 268, while Englishman Paul Casey (71) birdied the final hole for second place on 16-under.
Now with consecutive runner-up finishes in his last two starts this year, he's entering the Genesis Open with significant momentum.
Casey called Mickelson's effort "a phenomenal round of golf" but added: "It's not over yet". Before he won, he marked his 500th PGA Tour cut made on Friday. A birdie at the second was followed by eight straight pars before back-to-back bogeys at 11 and 12.
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