LPT: you can make a fort out of mattresses and couch cushions to help survive extreme cold if your power is out (Texans, this is for you)

Make sure you still have a tiny bit of airflow. I know there are plenty of problems that arise from extreme cold and lack of electricity, but this helps check off one basic need.

Edit: I learned this at a wilderness/urban survival camp. The less air you have to heat, the more efficient your shelter (think of how sleeping bags work)