WE have a broody who successfully incubated and hatched seven chicks. They were hatched the day before the first polar vortex round hit. We moved her and family into an elevated enclosed pen where they were plenty warm for the first week. THey are now into the second week, and we have moved them into a bigger, but still elevated and enclosed pen. The temperature in this pen has been around 40 -45 F during the day,, depending on the outside temperatures, and mom and chicks have been fine. It gets colder at night, but she keeps them under her, and we put a heat light on them all day during the day when we are around to monitor. I was planning on moving them into yet a bigger pen this weekend, which is enclosed by wooden five foot high walls, and the rest of the pen, including the top, is enclosed in poultry netting. The bigger pen is about 8 x 8 feet wide and has a dirt floor with about 6 inches of bedding on top. However, round two of the polar vortex is here and is expected to last for the next two weeks at least, with single digits to sub zero temperatures. The chicks, now almost two weeks old, have been fine, are almost fully feathered and the cold does not seem to bother them much, but obviously it's going to be colder when they move into the bigger pen, and also the outside temps will be colder, it's supposed to get down to -10 at night and single digits during the day, the coldest temps so far this winter. I can keep them in the smaller pen they are in now, and they will be warmer, but my concern is that it is going to start getting crowded as they are growing quickly. WE have NEVER had a hen hatch chicks in this kind of weather, I was amazed that she was able to hatch them at all. So I have no idea how the extreme cold will affect the babies, even though they have done ok so far, and will be bigger and have more feathers in the coming week. Will they be strong enough to endure the cold in the big pen, where they can move around more, have more space, and practice flying? Or should I keep them in the smaller, warmer pen for the next two weeks and hope that they can endure being somewhat overcrowded? Eventually their mom is going to have a problem keeping them all under her to stay warm, also....although they can still huddle together. And, by the way, we decided not to move the family into the house, for the same reasons,...they would have no where to go as they grow, as we don't have a big pen in the house, and the only option would have been to move them back out to the barn eventually, where they really would have to do some serious adjusting to temperature changes..