If the summer is anything like last year's, good sunscreen is a must. I spent four days prior to Summer Seminar touring Colorado and acclimating , and after having my hair cut short, I actually burned the top of my head, face, and neck. I agree with nolifepilot: sunglasses, chapstick, eye drops, and ALOE.
7258 feet ASL and a relentless sun will do a number with all of the outdoor activities.
On the packing list if I remember, it says its optional to bring a travel pillow. I highly suggest you bring a small pillow because if it is like last year, you sleep in a sleeping bag liner on the beds in the dorm because you are not given sheets/blankets or a pillow. My cadre gave me a pillow to borrow for the time there, but that's because he had one to lend out.
Hope this helps, good luck!
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USAFA Summer Seminar 2013
USAFA Candidate 2018