I don't think it was the dry heat so much as the energy expenditure from walking in deep sand and overheating from the direct sun.

From personal experience, I've found that the dry heat of the desert Southwest and eastern Columbia River Gorge is much easier to tolerate then the hot and humid climate found in south Florida. Provided, of course, that I have some shade. At 100+F in direct sun, it's like wearing my backpacking pack.

I find that high heat and high humidity really contribute dehydration, hyperthermia and other heat illnesses. But I suspect that dry heat may dehydrate just as rapidly but more subtly, since it evaporates more quickly and doesn't leave you feeling as obviously damp and sweaty. This may be more misleading, and therefore more dangerous.

You done gone and broke the code. :-)

To make a further contribution to what is clearly becoming a heated discussion - the heat loss from your evaporating sweat is cooling you down and therefore aiding your survival. But the process has its limits. As the temperature rises (in my experience, somewhere above 104F or so in a low humidity situation) you had better curtail activity and stop generating heat.

We probably should distinguish between the effects of heat and those of dehydration, which can be insidiously fatal at surprisingly low temperatures.

You're right.

A simple, easy medical test for dehydration is to take a pinch of skin from the back of the hand or wrist between your thumb and forefinger and lift it up from the surface. If the skin remains tented up above surrounding skin level instead of immediately returning to level, then the patient is dehydrated.

The real secret to managing dehydration is prevention. Drinking water upon waking and again before starting the day's heat exposure activities, and being encouraged to drink at regular intervals throughout the day, will help. Gatorade or other sports drinks often popular, but are really no better than water. Given a normal diet, neither sports drinks nor salt tablets are usually necessary. However, some people do eventually get tired of having to drink plain water, so some sort of flavoring can help them to maintain adequate fluid intake.

Also, one of the simplest and most effective interventions for mild hyperthermia or uncomplicated heat stress is to have the patient immerse their hands and forearms into a bucket of tepid water. This technique has been clinically validated, and is quick and convenient, since all you need is water and a bucket, no icepacks, no towels, no fans, etc. It's also easier to get some people, especially the Type-A's, to do that than to get them to lie down with ice packs or cold damp towels applied to their groin, armpits and neck, or accept other interventions.

Water may be bulky, but it keeps us alive!