Hiking may not be on the top of your list during a heat wave, but this hike takes you to a naturally cool region. Caution: It will still be hot, and any strenuous outside activity should be avoided druing a Heat Advisory. Know your limits.
If you do want to go, here is a description of a cool hike down into Crabtree Creek valley (which is naturally cooler) where you can explore the old Company Mill ruins (also cool).