Catdad,
I think there are individual differences in body heat regulation. You might have to find out for yourself what works best in our heat- thakn heavens it is not humid except late July through September (and now others are laughing at that statement given where they live, but its all relative.) Having said all that I find that Acrylic tends to be hotter than wool and pv coolest. I just have a 13 oz 8 yard and I have never sweated in it.
all the best,