I have not been in a downpour yet and I bought this as an emergency jacket to keep in my Travel bag. I made the decision after getting caught day after day in Hawaii with uncharacteristic downpours and looking like a dork with a plastic poncho that did nothing to keep me dry. It was also too hot to wear anything thick. This folds extremely small so it is perfect for that. I always wear a small but I had to exchange this for a medium. It was tight around my chest. (I am a C cup) it does keep you dry and keeps your dignity intact.