On June 9, 1999, about 1800 hours Pacific daylight time, a Cessna 172, N5577E, operated by Hillside Aviation, Inc., Redding, California, was substantially damaged in a collision with trees during a go-around at the Weaverville, California, airport. Neither the private pilot nor the passenger was injured. Visual meteorological conditions prevailed for the personal flight operating under 14 CFR Part 91. The flight originated at Redding about 1230 with a 3-hour stop at Eureka, California, and subsequent stops at Hyampom and Hayfork. The 60-hour private pilot reported that he obtained his license so that he could make routine trips of a 100 plus miles over mountainous terrain for business. He had made the roundtrip several times but had never landed at any of the four alternate airports along the route. On the day of the accident he decided to take a friend with him on this routine trip and checkout the airports on the way back. The first airport was closed so they overflew the runway at 500 agl. They landed at the second airport, then departed. At the third airport they performed a touch-and-go landing. The pilot informed his passenger that they would not be landing at the fourth airport, Weaverville, but instead they would perform a low-level flyby. According to the pilot, during his training the flight instructor had informed him that the accident airport was a one-way runway due to obstructions at the north end. According to published information you land on runway 36 and take off on runway 18 due to rising terrain and unfavorable winds. During the low-level flyby of runway 36 at Weaverville, the pilot reported that he experienced a strong downdraft about 15 to 20 feet above the runway, and he attempted a go-around into rising terrain with a slight crosswind. The airplane collided with trees about 500 feet beyond the runway end. The pilot reported that the wind was 300 degrees at 10 knots. The density altitude was calculated about 3,773 feet. Runway 36 has a 3.8 percent upgrade.