What are some things I need to know to be sure my backyard chickens make it through our COLD Maine Winter?

Image by Rachel Tayse
Update on backyard chickens at houndsinthekitchen.com/2010/03/15/update-on-the-girls/

Question by Dave M: What are some things I need to know to be sure my backyard chickens make it through our COLD Maine Winter?
It gets really cold in Maine in the winter. Usually no colder than 15 below zero for a couple weeks in February. With the wind chill, though it can reach close to 30 below zero. We usually also get a few feet of snow. This is my first year raising chickens in my backyard and I just want to be sure they’re well cared for.

Add your own answer in the comments!