We are going to begin working on our coop this weekend and I have a nesting box question. I live in central Minnesota and it can get pretty chilly in the winter, sometimes -50 with wind-chill for a couple weeks in the winter. With the cold winters we can sometimes get, would it be ok to have an external nesting box? I am trying to make sure there is plenty of inside room in case the girls need to be kept inside for an extended period of time. Thanks for any info!