About an hour prior to the flight, the pilot checked the surface observation report for nearby Chico (KCIC) Municipal Airport, which was about 5 miles to the northeast. He stated that it indicated an indefinite ceiling of 200 feet and visibility of 3 miles with fog and ground fog. An aviation routine weather report (METAR) for KCIC was issued at the approximate time of the accident. It stated: winds from 130 degrees at 5 knots; visibility 1 3/4 miles, mist; skies 200-foot indefinite ceiling; altimeter 30.25 inches of mercury. The pilot stated that the visibility was good on the ground. As the airplane took off and climbed, he realized that the visibility went to zero. He turned around and tried to get back to the airport. He descended to try and get low enough under the fog to see the airport. There were trees on the east side of the airport, and he tried to stay above them while looking for the runway. He was on left downwind for runway 14 and turning base. The right wing hit a branch, and the airplane went down. The right wing and empennage sustained substantial damage. The pilot reported no mechanical problems with the airplane or engine.