Feng's 67 was tied for the low round of the day thanks to the adverse conditions at at Stockton Seaview Hotel and Golf Club. It left her at 6-under-par 136 through 36 holes.
Feng will go for her second career LPGA victory in Sunday's final round.
Rookie Moriya Jutanugarn, who was the co-leader after the first 18 holes, slipped to a 2-over 73. She fell into a tie with Haeji Kang (69) for second place at 3-under.
Sharing fourth place at 2-under were Chie Arimura (67) and Anna Nordqvist (68).
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