I'm planning a trip to an arid semi-desertic area. Temperatures will be around the 90s and 100s and can go down to 40s or 50s in the night.Dry place. I won't be camping but I will be doing a lot of day activities.
Besides water, sunscreen, sunglasses and adequate clothes what would you carry with you? I'm specially looking for small details that I might be not considering, tips & tricks :-)

Thanks.