Summer is not a season typically associated with layering . When the sticky air outside feels like it could swallow you whole and the highlight of your day is taking a cold shower at 8 p.m., you don’t want to pile on unnecessary fabric—or, God forbid, knitwear . But as all great tastemakers know, a lightweight layer is often what separates a serviceable summer outfit from a sharper, more interesting one. Check your Pinterest, and I guarantee at least one outfit saved in your “the girl I want to be” inspiration bank has an extraneous scarf tied like a belt or a light cardigan tossed over sun-kissed shoulders. By no means, though, is this a decree to start stacking shirt sandwiches willy-nilly and to bring your thick winter knits out on 80-degree days—wearing as few pieces as possible remains the goal. Rather, the art of summer layering comes down to strategic placements and fabric choice.…