Heyyo! Little late to the party I guess. Lol
My first Moab trip was from late September-Early October of 2015. Let me start of by saying, the weather is damn-near perfect. The daytime climate is great and the nights are absolutely perfect. The stars are purely addicting. I spent 3-4 hours a night laying on the 80's roof staring up at them. If you haven't spent much time out west, they will blow your mind.
I have not been in June/July/August, however a few of the Techs I worked with in Golden, CO were big wheelers. One guy in specific was obsessed with Moab, and made trips 4 + times a year for over 20 years. He "practically raised his kids in Moab". Given, a 5 hour drive versus 25+ makes a huge difference in how choosy you are about dates to visit, even if it is heaven on earth. - Point of sharing this: He told me if I ever planned a Moab trip after mid June, or before late September; to expect to be miserable.
I spent a week in Moab at the end of March this year. Climate was decent. The days were cooler, and a few of the nights got uncomfortably cold/windy at points. Otherwise, another solid time to visit. Still wasn't as ideal as my late Sep/early Oct. trip. The stars were awesome, but only about half as visible, and trails were pretty crowded at points.