Victor Helmer, Star Route, Jim Thorpe, today urged hikers and vacationers in the Penn Forest area to be cautious of snakes in that area, their appearance being on the increase because of the hot weather. Yesterday at 4:30 p.m., Helmer, caretaker at the former Dr. Harold Frendt tract, now owned by the Philadelphia YMCA, killed a five-foot rattlesnake with 15 rattles. It measured four inches in diameter from head to tail.