Here in sunny Queensland, I have no problem wearing an 8 yard 22 ounce military in the summer (peaked at 47 degrees Celsius last year). Wool is a good insulator, so an 8 yard "tube" wrapped around maintains a body temperature column of air under the kilt. A cotton shirt will deal with the top and mixed fibre wool and cotton hose are comfortable. Forget the tee shirts, jackets and waistcoats, of course!