With an apartment you're a bit limited in what you can do for power/heat; you're not firing up a generator or anything like that.

If all you have are the two snakes in your profile and it's brutally cold out, I would put them both in secure tubs in the bathroom along with the small "Mr. Buddy" propane heater which is designed for use in small spaces to keep your snakes at an ambient temp of about 80*F. This will also help keep your pipes from freezing. This time of year I probably wouldn't do anything unless I knew the we would be without power for more than a day, like after a hurricane or bad thunderstorm with widespread outages.

Also a tip: you can make warm/hot water easily during the summer by putting it into a dark container in direct sunlight.