I think your heat packs (as used for shipping reptiles) should hold you over, or if you have a gas powered hot water heater, I used jars of hot water during
an ice storm power outage to keep my snakes a balmy 82*....but DO be sure you have cloth bags for each of them on hand, and as many ice chests as it
takes so they aren't too crowded...that will keep in the warmth really well. (My house was about 45* during that ice storm and I was wishing I could have
fit into one of the ice chests with the snakes...) I'll keep you & everyone who's in the storm's way in my "good thoughts". Sure hope it's not too bad.