Jack, don't forget about the
Donner Party here in California. It was no party! We have some cold weather here also but I don't care to put up with that kind of cold and live some place warmer.
The USDA hardiness zones are useful for determining the ability of a plant to survive but not necessarily grow well and fruit. The Sunset zones mentioned by microfarmer take into account both aspects.
Pete's E. maurelii withstood winter temperatures down to 22F (-6C) this past winter and he has photos in the forum showing it growing back fronm the corm with just a light layer of mulch for protection.