Hikermor ...
While I agree that a lot of the western US is pretty rugged, Arizona actually has one of the largest "changes" in ecosystems in the US. Something like 11 different ecosystems in the state, from desert to alpine mountain terrain. So it would be easy to start in Phoenix at 120 degrees at noon and end up in Flagstaff at 50 degrees at midnight in mid summer.

Kind of hard to pack when it's going to swing 70 degrees in a 3-hour drive, y'know?