It took an act of nature to slow down world number one golfer Jason Day in the second round of the AT & T Pro Am at Pebble Beach.

Day was halted by fog after 12 holes. He had fired seven birdies without a bogey, including a streak of four consecutive from the ninth through the 12th holes. Had he been able to finish the round and continue on that pace, he was in line to shoot 10 or 11 under par for the round.

The tournament has been plagued by weather. Jordan Spieth was one of the only golfers to complete his second round, leaving more than 100 of his fellow professionals waiting until Saturday to finish their second rounds.

The fog has generated calm conditions, with little wind and soft greens, meaning that the courses are vulnerable to the pros, with many of them walking onto pristine greens with six and 10 foot birdie putts that have been dropping as though the force of gravity has been dialed up.

Matt Jones, Cameron Percy and Geoff Ogilvy are also making strong showings.

When Jason Day eventually finished his second round, he had carded a 64, which tied him with Derek Fathauer for the best score of the round.