This jacket alone is great from 70 degrees to the high 40's. In the rain it stays warm if it gets wet and will keep you dry unless it is a downpour. In freezing temps works well with layers if you are active. It's heat levels are most similar to a fleece. It looks better, handles rain better, and is lighter than a fleece. It's not useful below 20.

I bought it as an insulation layer to put under my softshell when skiing. Most days it's great but when it gets supercold, it's like this layer isn't even there, so be aware of that. Although it is not as hot as I hoped I found myself wearing it every day walking around or driving or in the office as a sweater. It feels very comfortable even in warm temperatures.

This is one of the best jackets I own, one of my favorite pieces... And I've tried them ALL. This thing weighs nothing, packs down to the size of a rain shell, totally windproof, water resistant, and extremely warm once the primaloft has expanded to full capacity. When it gets really cold, I layer my Arcteryx Hercules jacket under the Kappa Ar and it shields me down to the negatives. It has Gore windstopper shell, fits/looks like a regular soft shell jacket (quite slim), and dosn't swish and swoosh like down jackets with nylon shells. The fact that the insulation is bonded directly onto the shell means this is not quilted, so you don't have to look like the Micheline marsh mellow man. I can't say much more, this has retired many other shell/fleece combo jackets i have... What more can you ask for... an insulated gore windstopper shell that fits like a fleece jacket and weighs a little more than air. My very next jacket is going to be the Kappa SV from arcteryx.

Living on the west coast I don't need extreme insulation. This jacket is perfect if you want windproof water-resistance in a good fitting/looking AND light package. If you want to keep warm in a light jacket and maintain good flexiblity this is it. Highly recommended!

Don't get me wrong, this is a very nice jacket, but the fit seems weird, at least on me. The inside is insulated with sort of a "gray" color. The collar on the jacket is low, and will not keep your neck warm. Overall, it's a good jacket, that has warmth to it with primaloft. I had to return the jacket because of the sizing issue.