>>2333885High five. Was at Joshua Tree exactly a week ago. No morning dew. Went from ~85° to ~45°. Not a super extreme fluctuation. I used the "fly" on my Walmart tent knowing it's not water proof, as I have very little desire to go /out/ in the rain as it is miserable for me.
To the other anon, I made myself clear. Mountains/ high elevations can have sporadic weather. Yet... When I was in Bryce Canyon Utah, the lady at the gate said it's going to start snowing at 4 or 5 pm. Sure as shit, 4:05PM a light dusting and by 5 it was a snow flurry.
Weather forecasts are more accurate than they've ever been. Knowing is half the battle, don't battle uphill in the rain.