According to the pilot, the purpose of the flight was to deliver the airplane to a new owner in California. Prior to departure, he checked the weather via computer and had the airplane refueled. The pilot reported "the flight was routine and I was cruising at 8,500 [feet mean sea level] and 80 [miles per hour indicated airspeed] with the landing gear retracted in the floats. Approximately 55 minutes into the flight and over flat terrain with no trees...I encountered an extreme wind gust which caused a severe right yaw, a left bank of approximately 45 degrees, and severe sink...Engine power was full. I could not regain aircraft control or stop the descent. The yaw attitude switched violently from right to left yaw." Subsequently, the airplane impacted terrain and was destroyed by post-impact fire. The airplane came to rest in a open field at an estimated elevation of 7,500 feet. The pilot's calculated density altitude was 11,800 feet, and he reported the wind was from 220 degrees at 15 knots, gusting to 24 knots. During a telephone call with the NTSB investigator-in-charge on the day of the accident, the pilot declined to report the accident circumstances; however, he stated that the airplane had no mechanical problems during the flight. The pilot reported he had accumulated 4 hours in the accident airplane. The pilot, who was the sole occupant, sustained minor injuries.