The incident occurred July 14 at about 8:30 p.m. near Parma Way and Covington Road, but the victim reported the incident only recently, Sgt. John Korges said.
He said victims of sexual crimes sometimes don't come forward right away.
"The unfortunate aspect is it's not like a house burglary," he said. "It's a different type of victimization."
Citing the juvenile victim's privacy, Korges declined to give her age but said the girl is in her early teens.
The suspect is described as a man in his early 30s, about 5 feet 10 inches tall. He had a medium build, a mustache and short black hair, according to the victim's description.
The man was driving a dark green Ford Explorer with a roof rack, tinted passenger windows, Firestone tires and dual exhaust pipes, according to police. The SUV is believed to be a model built between 2003 and 2008, and has a partial license plate of 5KG.
Anyone with information on the incident is asked to call police Detective Susan Anderson at (650) 947-2770.