Rex,
Those may be a new version of the shirt I use. I don't know for sure. I got one of mine out of the closet and the label says "100% cotton lining: 100% polyester", whatever that means. Mine aren't hot at all. They have a vent in the back that the Oklahoma wind blows through and you know from experience how nice and cool an August breeze is here in Oklahoma about 4:00 in the afternoon on a nice sunny day.