Texas International Airlines Flight 926 sustained damage when it struck a tree and two power poles, 12,000 feet short of the runway threshold, during a predawn instrument approach to Harlingen Airport, Texas. After the aircraft struck the tree and power poles, the flightcrew executed a missed approach and proceeded to Houston Intercontinental Airport, Texas, where a safe landing was made. The aircraft sustained substantial damage as a result of striking the tree and poles. There were no injuries. TXI Flight 926 was a regularly scheduled domestic passenger/cargo flight which originates at McAllen, Texas, and terminated at Dallas, Texas, with scheduled en route stops at Harlingen and Houston, Texas. Reported weather conditions at Harlingen at the time the accident occurred were: sky partially obscured, visibility 1/2 mile in fog. The Safety Board determines that the probable cause of this accident was the continuation of the descent, during actual instrument conditions, through the Minimal Descent Altitude and into ground obstructions as a result of inadequate flightcrew monitoring of the aircraft altimeters. A contributing factor was a lack of awareness by the flightcrew of the actual meteorological conditions, caused by crew fatigue, and company workload priorities which prevented normal air-to-ground communications and deferred the dissemination of essential meteorological information.