If you have a small flock, get a nylon puppy pen and bring them inside. Put a tarp under the pen and used pine shavings in the pen. Larger flocks may do well in such extreme weather because the bodies do produce heat, and the flock can huddle together to keep warm. Keep extra water in the house (I use gallon jugs) to carry water to your flock. Remember to maintain ventilation as it is necessary to keep the air moving to prevent condensation from building up in the coop. Keep your chickens well fed and some Rooster Booster in the feed will provide extra calories needed to maintain body temp.
