I am in Virginia and I had a Dutch Bantam hen who would hatch no matter what the weather. She hatched any time of the year--she has had new chicks in January. She passed away about a year ago unfortunately but I never had a problem with hatching in the winter. I did use a heat lamp just in case since I wasn't in the coop to watch and make sure they were all underneath her. The hens are very intuitive and the chicks make a special peep when they are cold, she will take care of them! Good luck!