I have kept pots with lily bulbs out side and in my unheated garage. Outside I placed old blanket on top of the soil and then put the pot into a large trash bag and kept it on my covered porch. The point is to not let it get wet and freeze. In my garage I put my pots in large trash bags(mostly to keep rodents out) and about once a month give them just a very small amount of water...like a 1/4 cup. Again you don't want them to be too wet and rot or freeze. I do keep them close to the garage door to keep them as cool as possible.
I start checking them around March. They have usually started to sprout a little. As it warms up I put them out uncovered on nice days and back into the garage at night until it is dipping below freezing.
