When is it "cold" for a chicken?

So I live in the Raleigh NC area and we haven't had any really cold weather yet but we have some concerns about the winter and traveling. We have a little coop with attached enclosed run. We only have the 3 chickens so it seems plenty big enough. My hubby put down hardware cloth for safety and when we travel for a weekend we don't worry about the chickens at all, we just leave the door from the coop to the run open so they can go in and out. When we get back they really appreciate getting to run around the yard but we think they are fine for 3-4 days in their space.

My concern is now that it is going to get colder. Can we leave them for the weekend and leave the little door to their coop open at night. Seems I don't need to shut it if it is above 40 degrees but when it gets down in the 30s I worry they might get too cold. If we are away, then they can't get out. Could we use a "heavy" fabric over the door? I son't know if they would like having to go through the fabric or not. Should we put plastic around the run when we go away and keep leaving the door open? We could ask a neighbor to stop by but that seems a bit of a pain when it is simply to open and close the door morning and night. Plus we want to wait to impose on the neighbors for when we go away for a real vacation and need them to actually feed and water the girls. Thanksgiving is coming up and we are looking at being away for 4 solid days. They will have plenty of food and water but I need to figure out if we need to do anything for the cold temps at night. Thanks for the help!

I would be very concerned about the water freezing when you are gone and not having access to fresh water. If you go away you may need to have someone check on them a couple of times a day to make sure they have water to drink (not frozen) and that they have not run out of food.

For over thanksgiving it probably won't even get down to freezing. We have plenty of feeders set up when we go away and I track their consumption of food and water the 2 weeks leading up to a trip in case we need to add more. Right now we are mostly worried about the door issue. Heck, down here it may not even go below freezing over Christmas. We sometimes shop for our Christmas tree in shorts! Thanks for you reply though! We keep reminding our 11 year old daughter (they are really her chickens ) that water is even more important than food!

In that case if you're not worried about water freezing then your chickens should be fine as long as they are able to keep out of drafts. Just make sure there is plenty of bedding in the floor of the coop to help insulate.