Heat pumps don't work when the ambient temp is below freezing.
https://www.motorbiscuit.com/electric-vehicle-heat-pumps-improve-range-hot-weather/
Originally, heat pumps were designed to work in weather 30 degrees and above. Now, however, they can run in temps well below zero. While they initially weren’t the component of choice for EVs, they’re now beginning to be installed in many models.
Wrong. The limiting factor is when the working fluid will no longer vaporize....which happens well below the freezing point of water (depending on which working fluid the system uses...Freon, ammonia, or propane).
They still work but auxiliary heat must be applied. Many have used thermal heat storage or if water supply is not an issue they use thermal energy from water. The point is though they require auxiliary heat to work below 32 degrees. My home in Southern Oregon uses heat pumps exclusively, we have few days below 32 but the heat pumps keep up by turning on the heat strips built into the units. No natural gas available here but for the creative types you could provide auxiliary heat with firewood, at least for now.