There is monsoon cloud buildup near sunset with the mountains in the background and desert cacti and vegetation in the foreground. The sun has rays breaking thru the cloud cover. I try to carry a camera with when leaving my house during monsoon season not knowing if there will be lightning or other storm buildup while I'm out and about. I was heading home through the Tucson Mountains, just outside the national park boundary and saw this sky buildup and immediately searched for a place to pull over and shoot.