This is my first winter with chickens. I'm in Southwest PA and we just got our first snow. I usually let my flocks out of their coops in the morning to free range and they return at dark. Now that the snow is here do I still let them out? I know they can take the cold but I'm worried about their feet getting frostbite. I leave the coop doors open but they never go back in until dark. Even yesterday when we got light snow and it was very windy they stayed outside.