In Zone 7 I wouldn't worry too much about the cold and potted plants. Snow is no big deal, freezing temperatures are! Roots are the most fragile part of a plant and when plants are in pots those roots are subjected to the cold. If that soil is subjected to freezing your plants are in danger.
Snow does not mean freezing temperatures and frozen soil. Snow is actually a great insulator of plants and their roots during the winter.
Zone 7 is fairly safe for potted plants out of doors but for us to tell you one way or the other about safety of your potted plants, bulbs, we'd need to know more about your micro environment and where it is that you live. What soil did you use in those pots? What fertilizer was added? How do you manage water?
You most certainly can protect your plants in pots out of doors using Reemay to cover the entire plant and pot to be on the safe side. Please tell us more about your zone and location and management practices for us to be able to be more definitive.