The pilot reported that when the flight was 15-20 miles south of the airport, the airport’s automated weather station broadcast indicated that the surface winds were light and out of the west. However, subsequent broadcasts indicated that the wind was from the north and then out of the south. The pilot canceled his instrument clearance before entering a left downwind for runway 18 (4,001 feet by 75 feet). He stated that after turning onto final approach he applied full landing flaps and deployed the speed brakes in order to bleed off some excessive airspeed. As the airplane passed over the 1,000 foot runway distance marker, he recognized that the airplane was landing downwind. The pilot stated that the airplane touched down after crossing midfield, after which he briefly applied brake pressure before deciding to abort the landing attempt. He kept the airplane on the runway as it accelerated, rotating and achieving liftoff toward the end of the runway. The airplane then impacted one of the 18-inch high runway end identifier lights located at the departure threshold. The pilot stated that after liftoff the engine did not appear to be producing maximum power and that there was a continual drop in airspeed. The pilot was unable to establish an adequate climb, so he made a left turn in an attempt to avoid some trees and an elevated roadway. The airplane continued to lose airspeed as it descended into a tree line located about 1,000 feet off the end of the runway. The pilot noted that the lack of engine power was likely the result of an improper propeller and/or mixture control setting during the aborted landing. The pilot also noted that he did not retract the wing flaps and landing gear during the aborted landing attempt. He further stated that his delayed decision to abort the landing contributed to the accident. A postaccident inspection did not reveal any preaccident anomalies that would have prevented the normal operation of the airplane or its engine. Local weather stations indicated that the prevailing wind was an onshore breeze from the north between 2 and 7 knots.