The private pilot departed his home airport in his tailwheel equipped high-wing airplane. The destination airport was equipped with a single paved runway that measured 4,300 feet by 60 feet. According to the pilot and a ground witness, the runway was plowed full width, but there was about 1/2-inch of snow on the runway, and about 18 inches of snow on the terrain adjacent to the runway. Also, according to the pilot and the witness, the landing approach to runway 30 was normal, and the airplane touched down in a three-point attitude close to the threshold, and on the runway centerline. The airplane became airborne again, drifted to the right, and touched down off the runway, in the deeper snow. The pilot added power to recover, but the airplane main wheels sank into the snow, and the airplane nosed over onto its back. The pilot was uninjured, but the airplane sustained damage to the horizontal and vertical stabilizers, and to one wing. The pilot noted that no mechanical malfunction or failure contributed to the accident. The pilot stated that the airplane was upset by a wind gust, and that if he had been aware of any gusts prior to landing, he would have conducted a wheel landing instead of a three-point landing. The Federal Aviation Administration Airplane Flying Handbook (FAA-H-8083-3) recommended the use of wheel landings in "turbulence or in crosswinds." The only airport windsock was located about midfield, on the southwest side of the runway. Based on their windsock observations, the pilot and ground witness estimated that the wind at the time was about 6 to 8 knots, out of the south or southwest. Witnesses familiar with the airport reported that the windsock generally provided reliable indications of the wind conditions, but trees partially sheltered the windsock from south/southwest winds, and therefore those winds were not always accurately indicated by the windsock.