A down jacket is (literally!) light as a feather, while keeping you wonderfully warm. How is that possible? Well, down provides lightweight insulation. In fact, there is no other material with a better weight-to-heat ratio! A down jacket is therefore ideal on cold days. By the way, this kind of jacket is very comfortable to wear: your body heat is regulated while the jacket is also very breathable. So no clammy feeling! The only downside: a lightweight down jacket is not waterproof. But in dry weather, it’s a real winner.