I learned after my first summer trip a couple lessons beyond basic moisture wicking clothes- cooling hat (branded Mission or something like that on
Amazon, make it wet and it cools you down),
UV umbrella, cooling towel. Try them and see what’s best for you.
And proper footwear! Second summer was hotter and I learned I had the wrong sandals. I was using Keens that had a cover over the toe portion and in high heat it turned that part of my sandal into a mini-oven and my toes swelled like crazy. Switched to sandals that didn’t cover the toes and it helped keeping down the swelling.