217 days of sunlight for SC, 286 for tucson. Also the light has more energy in Tucson:
I have similar problems at my place--we are that orange area just up from the Delta in California.
Plastic water fountains do not last a summer here. It is likely worse in Arizona for sure.
I thought about the qty. of days without cloud cover. It is a desert, LOL. I lived there. I am familiar with Arizona. I could not explain it from three years to three times in a year. That is nine tarps to one. It is more than sunshine is what I am thinking. There is no difference in intensity, just qty. because of cloud cover (or lack of). The distance from the equator is similar. I was wondering if the dry air made a big difference. The humidity there is much lower.