Are lightweight insulating jackets warm enough?

A: Well, depends on whether you're comparing apples to apples. Weight doesn't necessarily determine warmth/insulation—what matters is how thick a dead-air space the insulation creates. GoLite strives to give good, lightweight insulation by not stitching down the insulation as much as some makers, by using the lightest shell materials and zips they can find, and by cutting things pretty trimly. Result: The Six-Month Night Ultra-Lite Arctic Parka, for $99. It weighs two pounds, two ounces, and uses Polarguard 3D insulation. I'd compare it function-wise to L.L. Bean's All-Conditions Primaloft Jacket, which sells for $160 and weighs a bit more. Both are light insulated pieces—fine for plenty of applications, but not something I'd use much once it drops below zero. People who tend to be on the cold side may find them a bit thin at around freezing. And that isn't a knock on the garment—it's just that when it comes to insulation, the only certainty about how "warm" it will be is that you just never know.

Will it keep you warmer than other, heavier stuff? Depends on the stuff. I have a Feathered Friends Rock & Ice Parka that cost $600 and wraps me in about four inches of down-filled air space. My bet is that it's a good four times as warm as the Six-Month, which yields about an inch of insulation. But for $100, and for plenty of people, the Six-Month is all the insulated jacket you need. Just keep in mind that there are limits to what a few ounces of Polarguard can do.