Sorry for the delay responding, but it's pretty much as has been said: Acrylic kilts are warmer in hot weather than wool because they do not breathe.

I would say that from my personal experience, that is certainly more of an issue when it is humid, but it's still an issue even when it is not humid. The first time I ever had to change out of a kilt because it was too hot was in some hot, dry North Carolina mountains. That was a Stillwater Standard. I actually found shorts more comfortable, heat-wise.