What you should know: The layer to throw on when you're sitting around camp, or when you're active but it's really cold and dry.

Our pick: The North Face Radium Hi-Loft Hoodie. At just 16.6 ounces, you'll barely notice this in your daypack, yet once you pull it on, the high-loft synthetic garment is incredibly warm, even when it gets wet. [$190; thenorthface.com]