I returned it promptly so I can't tell you how warm, windproof, or water resistant it is but I can help with sizing. I originally got a large and it was quite baggy on me (6'0" 170lb) in the chest and arms. It was also quite long in the sleeves. I swapped it for a medium and the sleeve length is perfect and the fit is much more 'athletic'. However, it is abnormally short in the torso. My T-shirts stick out of the bottom. It's longer in the back but I wish it was that length all the way around. Makes me look pretty goofy.