It's only a hundred out, that's basically fall

Late afternoon in August, on the Katy Trail. A man in running shorts said to his friend, who was holding a water bottle like a rescue, "It's only a hundred out, that's basically fall." They ran. I was walking the other way, in the shade of a tree, and I will say plainly that running then was a mistake, and he probably knew it. I did not stay to find out how it ended.