The 19-year-old woman, from Vancouver, Wash., was reported missing from Canyon Creek Campground (located east of Amboy in the Gifford Pinchot National Forest) just after midnight.
According to Undersheriff Dave Cox with the Skamania County Sheriff's Office, the woman walked away from the campground around 5 p.m. Sunday.
She was in the nude and had only a fanny pack, compass and knife with her.
She was supposed to return that night. A friend reported her missing around midnight.
"We had a fairly mild evening last night with temperatures in the lower 50s," Cox said. "We have set up a command post in the area and currently are utilizing ground search teams in the immediate area in an attempt to locate her this morning."
Both Clark County and Hood River County are helping with the search.