As long as your chicks are fully feathered they will be fine. We tend to think our birds get cold like people do, but they are designed to be outdoors. They will huddle together to keep warm. The main thing is making sure your coop is draft free on cold nights, but still has the proper ventilation. They will learn to roost as they grow. I had a baby chick hatch in the coop in February during a cold snap...it dipped down to 5 degrees several times and I was worried to death. I named her Winter. She is a tough bird and is doing great. So don't loose too much sleep!