Welcome to our forum.
So, who out there is ready if an ice storm leaves them in the cold?How will you protect your hot tub and keep your house warm?
If you have a generator, just buy one of the ~$30 space heaters you can buy at your local hardware store. Make sure it has some sort of thermostat, even just low/med/high so that it will shut off if it gets to hot. Open up the equipment bay and put that in there and run it on low/med until you have power back. If there are vents, throw a heavy blanket over those to minimize heat loss. This should keep your spa from freezing for a few weeks.