Hardiness or Climate zones are used as a tool for gardeners and orchardists to guide in selecting appropriate trees for particular areas. The climate zones are determined by average minimum yearly low temperatures. This is only a general guide because your own individual location (microclimate) has a significant influence that the general zones neglect to recognize. These variations may suggest that the zone adjacent to you may be more appropriate.
Please use the USDA's Agricultural Research Service to find your Hardiness / Climate Zone.