USDA hardiness zones are more equipped to adress top kill temperatures (tissue damage , desiccation etc). Root kill temperatures are less robust, better place on ground since there is potential for geothermal heat to give up to 7F for the roots. It’s also advisable to heal with mulch around the pot up to rim for reduction in heat transfer, and moisture loss in the container. I’d place on ground and heal in once night temperatures reach 25F or below range consistently. Also near a structure to reduce wind and moisture moss that way.