The USDA plant hardiness zone map is a map of the United States that farmers and gardeners use to determine what plants do best in each geographic location. The map is divided into zones of 10 degrees Fahrenheit.
Users can click on their states on the map available on the USDA's website, select their states from a drop-down menu or enter their ZIP codes to see which hardiness zones they live in. The USDA bases its hardiness map on the average extreme low temperature from a 30-year period in the past. The map only provides a generalization of plant hardiness, as many factors can affect climates, including hills and valleys, concrete and asphalt surfaces, and proximity to bodies of water.