Where in Arizona do you live? Flagstaff is a lot different from Phoenix.
I agree with Wavery re Arizona sun - I spend half of each year in Scottsdale. But in case a car port is not on your "gotta get one" list, I can tell you that many of our members use covers from ADCO. As I recall, ADCO offers at least 3 different materials, so be sure to get whatever is most sun-resistant.
I also recall that ADCO makes choosing the correct size a puzzle. If you go by dimensions, most covers give you too much material, and the slack whips around in the wind and self-destructs. I ended up buying one that was listed as right for a Hi-Lo, item 12295, and it fit nicely. However, I'm not sure the Aqua-Shed material would be the best choice for Phoenix - maybe Tyvek would be better?
The Hi-Lo size also does not go quite all the way to the ground. This is good, because it encourages air circulation. A cover that goes all the way to the ground traps moisture, and as Wavery says, mold can result. So if the monsoon ever arrives, this open bottom will help tame any mold issues. Some more advice on sizing in post #6 here
https://www.trailmanorowners.com/for...ead.php?t=2046
Two warnings - perhaps you already know. First, if any part of a tire is visible below the cover, be sure to keep the sun off the rubber. Use a tire cover, a sheet of plywood, whatever. Second, the TM has some sharp points and edges, many in the hitch area, many more if you have the Winegard crank-up TV antenna. Pad these sharps! They will rip your cover in one season.
For more discussion, do a search in this forum on the word ADCO.
Bill