USDA Hardiness Zone Lookup Tool
Website owners, you can offer visitors to your site a fast, FREE, convenient tool to look up their USDA hardiness zone. TheVegetableGarden.info USDA hardiness zone database contains nearly 42,000 zip codes from all across the United States and is based on the latest USDA zone map. It includes all of the 11 USDA zones (1, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b, 11).
Try it out.