There is the smoke from California’s frightening fires to consider, and the dust kicked up by winds off the tropical storm front, and the contrast provided by incongruous ranks of rain clouds. Illusion may play a role.
But something happens to the blue in the desert sky this late in summer.
In June and July, the sky here fairly pulses indigo. But something fades that depth by September. Perhaps it’s the endless baking heat, irradiance desaturating the sky as though it was a plastic wading pool left to soak up a year’s ultraviolet.
Where once it was lapis and sapphire, the late summer sky fades to Kingman turquoise. Tinges of celadon, of rose and khaki.