Layer, even if you’re escaping to warm weather.

Think you won’t need to cover up while warming up? No matter how sunny your vacation, malls, museums, cinemas, and airline cabins are often air-conditioned to a wintry degree. The best bet is a lightweight, waterproof jacket; stuff this space-saver into your carry-on. A shawl-size scarf—virtually weightless and warm—is a woman’s best friend, and can act as a beach cover-up or a wrap.