Where does it get power? Does it heat, or just tell you it's cold?
In Tahoe, we would run a separate 20 amp gfci circuit to the spa and mount a plug in the equipment bay for a space heater. If running, the equipment bay will be warm, but if it gets cold the space heater kicks on. If you get power from the spa pack a gfci trip still screws you, so the extra circuit is crucial. Of course a power outage will still be an issue, but you can't have everything.