In essence, this fog occurs in late spring and early summer when warm air aloft traps cooler, moisture-rich ocean air below (the “marine layer”). The area’s prevailing westerly winds then bring all that moist air ashore as low-level clouds — fog with occasional drizzle — that usually burns off as temperatures rise throughout the morning.
There were no weather delays when Torrey Pines last hosted the U.S. Open in 2008, though fog has caused trouble for the Farmers Insurance Open, which takes place annually at the course in January. The 2013 version ended on a Monday when the third round was interrupted by fog, and last year’s tournament also was delayed a bit in the third round, though things ended on Sunday as planned.
After visibility improved enough Thursday that the golfers could see where they were aiming, the first groups teed off at around 11:15 a.m. Eastern, about 90 minutes later than planned. Though predicting when the June Gloom will strike can be tricky, the forecast for the rest of the weekend calls for sunny skies and little wind.