I keep a stockpile of handwarmers for power outages.
I'd cover the enclosures with insulated blankets and use the handwarmers as needed.

I don't recommend worrying about food for snakes in that situation.
Feeding with inadequate heating for digestion will be much more harmful to your snake than a month without food. Don't risk a regurge! Just wait out the power outage and concentrate on preventing hypothermia.