Who says that you cannot layer up when it is warm out side? I do it all the time, it is all about how you layer. For example, do not wear a merino wool sweater with a button-down shirt when it is 75 degrees outside, instead, go light. Pair a tank top with a button-down or flannel shirt–with the sleeves rolled up–think of it as a t-shirt that is cut open. And finish with your favorite jean and sneakers. Although it is fun to show some skin, it also cool to layer up.