I second what Ian says about apron slack and sporran weight. Don't skimp on fabric weight either just because of climate concerns. Wear a kilt with reduced yardage like a 5-yard knife-pleated or a box-pleated kilt. Wool breathes but if you sweat profusely in 16 oz. wool, you'll probably still sweat in 11 oz. Believe it or not, it gets very hot in the summer here, sometimes reaching over 40 C (with the humidity) and I find that only my upper body suffers from the shirt, jacket, and tie. Which I would still suffer with a suit on.