I don't have direct experience with quilts, but I know from my sleeping bags that the ratings are not true to the comfort level except under ideal conditions: new bag, wearing warm base-layer and wool socks, covering the foot end with a jacket, sleeping on an insulated pad, in a small tent. My kids from personal experience say if you expect temps around 30 degrees F, get a sleeping bag rated at zero degrees. Their reasoning is that over time the insulation loses its loft and provides less insulation. Be sure to pack the bag or quilt loosely when it's stored between trips rather than in a compression sack. I use a cotton laundry bag for that storage. I have been testing a 30-deg rated bag and a 0-5 degree rated bag. I'm still a little cold in the 30-degree bag when temps are in the low 40's. So, I say, go for more insulation than a 30-degree quilt if you really expect temps near 30. And get some warm base-layer clothing, wool socks, and a balaclava.