Staying active in negative temps

Does anyone else live where it's below zero for most of the winter? Today it was -28°F when we woke up (without the wind chill mind you) and I'm finding it hard to stay active. Typically I walk the dog every day since we can't bike in the snow obviously, and its too cold to walk him or go hiking like we do April thru October. I don't have a treadmill as we don't have room for one but what do you all do when its so cold?? I usually took the three cold months to relax but being pregnant I want to stay in shape.

Thanks ladies!!