Stacy Lewis fired a second round 69 to take a three-shot lead halfway through the Kraft Nabisco Championship - the LPGA's first major of the year.
Lewis has led a major before, the 2008 US Open, but ended up finishing third.
She shared the first round lead with Brittany Lincicome, whose par second round of 72 left her joint second with Jane Park and Yani Tseng.
Sweden's Sophie Gustafson was the leading European in seventh while England's Karen Stupples is joint 19th.
Other Britons to make the cut were Becky Morgan of Wales on one-over-par, two shots behind Stupples, and English duo Melissa Reid and Laura Davies on two and three over par respectively.
The players had to cope with temperatures of more than 100C and as a result the greens were watered for four minutes overnight.
There was a dramatic moment when Michelle Wie's opening drive hit a young girl on the head.
The spectator needed medical treatment and Wie said: "I thought I just hit like a sprinkler or a tree or something. The little girl was the last thing on my mind, but hopefully she's OK.
"I kind of was asking her if she was all right. Unfortunately I couldn't be with her until the paramedics came."