The three-time winner this season, a native of Norway stands at 3-under 141, one stroke better than South Korea's Eun Hee Ji (68), who was the only golfer in the 60s in the second round.
"I did grow up in Norway playing in very similar conditions to this," Pettersen said after the day's windy and cool round. "There is a reason why I moved to Florida. I prefer to wear shorts."
Former women's British Open champ Jeong Jang (72) and Seon-Hwa Lee (71) share third place at 1-under 143, and Hyun Hee Moon (73) is alone in fifth at even-par 144.
World No. 1 Lorena Ochoa (75) fell into for 12th place with five others at 3-over 147.