AT 2006 CDT, BEFORE DEPARTING SAN ANTONIO, TX, THE PLT OBTAINED A WX BREIFING. AT THAT TIME, HE WAS ADVISED TO EXPECT VFR CONDITIONS ON HIS FLT TO SAN MARCOS, TX, BUT IFR CONDITIONS WERE EXPECTED WHEN HE PLANNED TO RETURN AT ABOUT MIDNIGHT. THE PLT FLEW TO SAN MARCOS WHERE HE PERFORMED A COMEDY ACT FOR A NIGHT CLUB. HE BEGAN HIS RETURN FLT EARLY TO AVOID FORCASTED DETERIORATING WX. REPORTEDLY, LIGHT RAIN & FOG WERE PRESENT BEFORE THE ACFT DEPARTED SAN MARCOS. WHILE ON THE RETURN FLT, THE PLT WAS FLYING ALONG AN INTERSTATE HIGHWAY WHEN THE ACFT COLLIDED WITH 2 POWER LINE CABLES WHICH CROSSED OVER THE ROADWAY. THE ACFT THEN IMPACTED THE GROUND ABOUT 500 YARDS BEYOND THE POWER LINE & BURNED. THE CABLES WERE ESTIMATED TO BE 110 FT AGL BEFORE THEY WERE SEVERED BY IMPACT. A WITNESS, WHO WAS A PLT, ESTIMATED THE ACFT WAS FLYING ABOUT 75 TO 100 FT AGL BEFORE IMPACT. HE ESTIMATED THE CLOUDS BASES WERE ABOUT 200 TO 300 FT AGL & SAID THERE WAS RAIN & SLIGHT FOG IN THE AREA. REPORTEDLY, THE PLT STARTED TO PULL UP JUST BEFORE IMPACT.