Wore this shirt in the Nevada desert for a training. Cold morning (wore Vertx sweatshirt) High heat of the midday... bring it on. Never had any issue with heat, uncomfortable seams, or funky sleeves flapping around my arms (like some polos are prone to do). The fit is athletic, and while being extremely functional, offer a great look when not engaged in strenuous activity. Being somewhat tall, I would yearn for a slightly longer length... but can't really complain.