We invested in something like this. 👆. They're emergency heat packs that once activated, can last a few days. They get warm but not hot enough to hurt your snake. Put your snake in a tub with air holes, wrap this in a rag or napkin, put it in the container with him, and he'll be fine. If you're worried about humidity, you can either spray him down by hand every day or put wet, balled up napkins also in the container with him. This is how I help them if they have trouble shedding. You can do it in the meantime while you wait for the power to come back on.
I use a thermostat with heat mat. I found this thermostat on Amazon, it's just under $20. https://www.amazon.com/dp/B01I15S6OM/ref=cm_sw_r_sms_apa_i_PVxVEbFN9SSF0
I've had it for a year and it's still going strong!