The cold desert
It gets damn cold in the desert! I was just backpacking last month in the Gila Wilderness (NM) and was able to enjoy great days of hiking and wonderful temperatures, but had to keep in mind that the nights would be cold. Oddly enough, I was two days into my trip when the well known trail runner was found after several days of searching. I believe it was the cold that got him in trouble, but that is my speculation. Not sure if "they" really know what happened.
The Dixie (and Escalante) are no different. Take care when choosing a bag for your nights out.