Morning hours (6 AM-9 AM) are absolutely the best. Trained in Tucson, ran first Marathon in Phoenix.
Hell @LisaG this is definitely one of the great questions for runners! I've lived in AZ for about 3 years now, and also ran longer distance runs/triathlons in Southern California too. My favorite joke is "you can workout year round in the desert....you just can't sleep in!"
As one person has said, early morning runs will be best when temps are mild. I also have a good friend who runs ultras, and she runs late at night with a training buddy (if you're a night owl, this is a good option).
One other suggestion- buy a hydration belt or running specific pack (Nathan, Osprey, and REI make one). It might sound like more gear, but they are genuinely designed to stay in place better than a regular hydration bag, which prevents chaffing. I also used to drive my long runs first and find parks with drinking fountains along the way where I could refill my bottles.
Finally, I load up on sunscreen, lightweight long-sleeve sun shirts, and keep a few electrolyte supplements (gu packs, cliff shots, etc) in my running pack/belt. For me, some form of music was always good to take my mind off the heat too.
Hope this helps, and good luck!
Hi @LisaG, Where are you currently training vs where the half marathon is? Is it on the trail or on pavement the entire time? Is it in the desert itself or just desert heat?
A couple of other tips in addition to the ones @REI-JimL said that helped me when I was training and running in Death Valley was to wear gore-tex or waterproof shoes and short running gaiters like these https://www.rei.com/product/137230/kahtoola-instagaiter-low-gaiters that kept the sand out of my shoes when I was off pavement. I would use two pairs of shoes depending where I was running, and I'd use either the ventilated or waterproof kind. If it was a sandy area, I hated having to stop and empty out my highly ventilated shoes so I just wore thin socks and gore-tex running shoes. If it's pavement, that's less of a problem but I'd still recommend the gaiters if it's sandy nearby.
I'd also recommend a buff or face protector in case a sand storm kicks up https://www.rei.com/product/146017/buff-coolnet-uv-multifunctional-headwear.
Plus really good lightweight sunglasses that wrap and keep maximum sun out of your eyes to prevent eye fatigue and a really good lightweight running hat to keep the sun out of your eyes and off your face.
Electrolytes, electrolytes, electrolytes! Really try to breath in and out of your nose the entire time. Any time you drink, make sure it has electrolytes since you'll be sweating out salt, and might not even know you are sweating due to the high dryness. If you need any help with electrolytes or have any more questions about them, let us know!
I'm stoked you're doing this! Hopefully even with the "shelter in place" restrictions your half is late enough in the year that it's still on! Best of luck and let us know how else we can help!