On April 27, 2003, approximately 1100 mountain daylight time, a Cessna 182, N5595B, impacted the terrain during an attempted precautionary landing near the shore of Box Lake, Idaho, which is located about 10 miles northeast of McCall, Idaho. The private pilot, who was the sole occupant, received serious injuries, and the aircraft, which is owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 91 personal flight, which departed Caldwell, Idaho, about 90 minutes prior to the accident, was being operated in instrument meteorological conditions (IMC) at the time of the attempted landing. No flight plan had been filed. There was no report of an ELT activation. According to the pilot, while he was en route to Copenhaver Ranch Airstrip, he entered an area of rapidly building cumulus clouds. Although he climbed to 14,500 feet in order to attempt to fly over the top of the clouds, the pilot found that the clouds were building faster than the aircraft could climb. He therefore inadvertently entered the cloud formation and soon encountered icing conditions. As ice began to accumulate on the aircraft, the pilot entered a rapid dive, and descended to about 9,000 feet. After he leveled off, ice continued to accumulate, and the pilot felt the aircraft was near stalling. About that time he saw an opening in the clouds, and observed what he thought was Box Lake. He therefore descended through the hole and found himself in a heavy snowstorm over the lake. He flew around the lake a few times, but could not find a way to escape the instrument conditions. Then, because more ice was accumulating on the airframe, the pilot made the decision to attempt a precautionary landing near the shoreline of Box Lake. During the touchdown on snow that was ultimately determined to be more than ten feet thick, the aircraft collided with hidden obstructions and flipped over. The pilot was ultimately rescued two days later by snowmobilers who inadvertently came across the wreckage. According to the pilot, there did not seem to be any problems with the aircraft's engine or flight control systems.