The pilot stated that while attempting to land in heavy rain and low visibility, the airplane collided with trees to the right side of the runway before descending and impacting the runway. The collision damaged the left wing, collapsed the landing gear, and substantially damaged the engine firewall. A Federal Aviation Administration inspector reported that the airplane's first impact with the ground was 68 feet from the tree impact. The pilot did not report any mechanical malfunctions or failures with the airplane prior to the accident.