The event was canceled last year because of rain, and there was more rain Friday. Players were forced off the Nashawtuc Country Club course twice for a total of three hours, but the first round was completed.
Watson made three straight birdies beginning at the fourth.
"I didn't feel comfortable with my swing early, but my old friend Byron Nelson once told me when you don't feel comfortable you concentrate more," Watson said. "I did that. My swing felt good after the first delay. I putted well today too."
Larry Nelson, a two-time winner of the event, shot a 68 to share fourth place.