Sidewinder. Should be C. cerastes cerastes in our area, but the tail coloring is what I would expect for C. cerastes laterorepens.
Observed wandering through desert scrub at 23:07. SVL approximately 61cm.
Crotalus cerastes is a venomous pit viper species belonging to the genus Crotalus (rattlesnakes) and found in the desert regions of the southwestern United States and northwestern Mexico. Three subspecies are currently recognized, including the nominate subspecies described here.