If you are going to work and/or play in desert conditions, you want to be an early bird. It is best to get going by 4:30AM to take advantage of the relative cool.

Sometimes during SAR operations you don't have that option. I and my partner once started on a trail at noon. Temp was 91 at the outset,with a five mile climb up a southern exposure, fortunately with a guaranteed water source at the top. We carried two and one-half gallons and reasonably full rescue packs.

When we reached the stream, we had consumed all our water and were quite thirsty, consuming about a quart each from the babbling brook. Fortunately we had gained enough altitude and it was later in the day, and we were in a shady canyon, so conditions ameliorated considerably.

P.S. We did find our victim, seriously injured, and extricated him the following morning