I guess I just don't understand what the chart is attempting to show. Maybe it's of more use in areas that are a little less homogeneous during the hot and cold month. Here, if it's 95 it may as well be 105 with heat index...which is a large portion of the summer. Not much difference in 95 and 99. It's hot, the air is thick and being outside is miserable. We've already gotten up to 99+ here. I'm guessing the chart is telling us certain days, to expect certain temp ranges? That's the best I can figure it. Having studied climatology for awhile, I guess maybe I am trying to overthink this, and what is painfully obvious to me isn't so to everyone?