Depends on how hot and humid it is outside. Even in breathable clothing like Nike Dryfit or any of the thousand knockoffs, in 90+ degrees, high humidity weather, a backpack blocks perspiration evaporating off. It literally becomes a hot spot on your back. He did have one tip I don't entirely agree with to use Vaseline, but instead I use Glide just because I don't care for the consistency of petroleum jelly. Although he mentions long sleeves shirts and a hat with neck guard, he said nothing explicitly about skin or eye protection; people in the sun day after day should be wearing polarizing lenses and high SPF clothing along with sun screen.