So when you decide to go to death valley in August and it is 135, these simple tips might help make your trip a little more enjoyable. I have been in tons of heat camping situations, I even lived in a tent for an uninterrupted 5 months over a summer in the New Mexico Desert. I have learned a few things about keeping cool. Here is my list of ways to beat the heat:
Become friends with the shade. When I was in New Mexico I used to carry a Tyvek tarp that I put grommets in to make a porta-shade. Tyvek worked like a charm because it is super tough, super light, and white, which helps it diffuse heat. This addition to my pack was worth the full 13 oz. In addition to some 3mm cord, it can be your best friend. Remember that in dry climates the shade can make a 20 degree or more difference.
Keep hydrated. Seems simple, but it isn't always, when you sweat, you lose water, and if it is really hot, the sweat will evaporate so fast that you may not even feel it. So you need to keep drinking constantly, even if you don't think it is necessary. In fact, You should know that once you feel thirsty you are starting to get dehydrated. Also when you sweat, you lose electrolytes. If you don't replace them, your body can no longer retain the water you drink. To replace them there are a variety of options, one that I fancy is Camelback Elixir.
Move at night. Moving makes heat, so to keep cool, staying still helps immensely. Try to stay still and in the shade during the hottest time of the day usually 2-5pm. Start your days early. If you can't finish by noon, chill out until the evening hours and finish your hike as it cools off. Your pack will make you hotter, and so will hiking. If you get stuck be prepared with a book, a deck of cards or something to do.
Dress Light. Keeping cool with good performance clothing from a company like The North Face can help keep you from getting too hot. Something that gives a high UPF rating to help block the sun, and something that is lightweight, breathable, and not too absorbent. Patagonia Clothing also makes Capiline, a great product for this purpose.
Put all your water inside your pack. Putting your fluids inside your pack opposed to in the outside mesh pockets may seem inconvenient, but it will keep it out of the sun's rays, so it stays cool throughout the day. There is almost nothing worse than trying to force luke-warm water down your throat in 120 degree weather.
Find a Breeze. The cooling effect of a nice cross breeze is quite magnificent. Thus, you should try to pick a rest spot where you will get some quality cross wind, it will keep you cool and comfortable, if you've got your Tyvek, it should be easy to find a spot almost anywhere with both shade and a breeze.
Eat cold food. Eating warm food will raise your core temperature, making you feel hotter than ever. Eating food that does not require heating will help you stay cool. Fruits have a high water ratio also, so they help to cool you off and quench your thirst.
Cover your head. Wearing a hat is a fantastic option, it helps keep your head in the shade which is a major influencer in how hot you feel, but it also helps your head stay cool. A quality hat with wicking properties will help keep your head cool and comfortable. For super hot situations when you have an abundant water supply, you can drench the hat in order to cool off your head.
Use that bandanna. A bandanna to cover your neck can be a great addition. take a white or lightly colored one to shed the sun, and get it wet if you have lots of water, keeping your head and neck cool will help more than anything else.
Expeditions in the desert can be fantastic if you know how to handle the harsh weather. The desert has its own type of beauty and serenity. As Edward Abbey said, "Strolling on, it seems to me that the strangeness and wonder of existence are emphasized here, in the desert, by the comparative sparsity of the flora and fauna: life not crowded upon life as in other places but scattered abroad in spareness and simplicity, with a generous gift of space for each herb and bush and tree, each stem of grass, so that the living organism stands out bold and brave and vivid against the lifeless sand and barren rock. The extreme clarity of the desert light is equaled by the extreme individuation of desert life-forms."