Replying to Weather Ratings for Outerwear

Im checking out this orage jacket from last year and its 5k/5k, as far as i can tell. I live in Ontario and the lowest temp it got to last year was between negative 20 and 30 degrees CELSIUS (canadian). This was on the coldest day, so it wont always be like this. Is 5k/5k enough for a day of skiing? I dont want to be freezing. Maybe if i layer enough? I wish i could tell the jacket name, but i dont remember it, and cant find last years orage catalog online. Its the one with the green swirls.
Thanks alot.