This jacket is advertised as windproof with a modicum of water resistance. It relies on the water shedding properties of the fabric which seems to work by magic and will let standing water through like a sieve but in practice offers full protection from the rain which I didn't expect. I tested it (unintentionally) in a 2 hour torrential downpour and it didn't let in a drop. I bought it as a windproof/get-you-home emergency shower jacket but I now have full confidence to take it out on rainy days as well. My only reservation is that on dry windy days when I'm getting up a bit of a sweat it doesn't breath that well even with the under-arm and back ventilation vents, and became damp on the inside quite quickly. I guess you can't have everything in a jacket that folds down into such a tiny pack. The medium size fit me well with just a bit of wind flap on the sleeves but no riding up at the back. I'm a near six footer 65kg skinny cyclist and find often these garments are either too big for my height or too short for my weight but this is as good a fit as I have found.