THE PLT & PASSENGER HAD FLOWN FROM BERMUDA DUNES TO YUCCA VALLEY, CA ON A BUSINESS FLT. REPORTEDLY, THEY TERMINATED THEIR BUSINESS EARLY BECAUSE WX WAS BUILDING OVER THE MOUNTAINS BETWEEN YUCCA VALLEY & BERMUDA DUNES. WHILE ON THE RETURN TRIP, THE PLT REPORTED THAT HE HAD PROCEEDED TO A POINT WHERE HE HAD BERUMDA DUNES IN SIGHT, BUT ELECTED TO DIVERT BACK TO THE HIGH DESERT ARPT (NEAR YUCCA VALLEY) TO OBTAIN FUEL. AT APRX 1420 PST, THE PLT & PASSENGER TOOK OFF AGAIN FOR BERMUDA DUNES. SUBSEQUENTLY, THE ACFT IMPACTED RESING TERRAIN NEAR THE TOP OF A MOUNTAIN RIDGE ALONG THE EXPECTED ROUTE. SEVERAL SOURCES REPORTED THAT THE WX HAD DETERIORATED IN THE VICINITY OF THE CRASH SITE. THE OWNER OF THE HIGH DESERT ARPT STATED THAT WHEN THE ACFT DEPARTED AFTER REFUELING, THE WX TOWARDS PALM SPRINGS WAS IFR. THE OWNER OF A HELICOPTER AG OPERATION NEAR DESERT HOT SPRINGS, STATED THAT THE WX BUILD-UP OVER THE MOUNTAINS WAS NOT CONDUCIVE TO VFR FLT OPERATIONS.