Well, when eating dessert, I don't wear anything special unless I'm going to a fancy restaurant for it, in which case I might wear something more dressy. What kind of dessert do you plan to eat? Sorry, couldn't resist!

Seriously, for hiking in the desert, I'd take something that kept me covered from the sun but otherwise well-ventilated, plus a couple of cotton bandanas that I could soak with water frequently and drape over head and shoulders to help keep me cooler. Also about 2-3 times more drinking water than I could possibly imagine I would need. I'd also get out on the trail at the crack of dawn and stop in the shade by noon, possibly resuming the hike after sunset. I'd try to route a desert hike to finish where ice cream would be available for dessert, too!