About an hour prior to the flight, the pilot checked nearby weather, which indicated an indefinite ceiling of 200 feet and visibility of three miles with fog. The pilot stated visibility on the ground was good and took off. As the airplane climbed, visibility went to zero. He turned around to return to the airport, and descended to get under the fog. 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, turning base, when 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.