The USDA Plant Hardiness Zone Map (PHZM) is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. The most recent revision was prepared by the PRISM Climate Group at Oregon State University, and was released by USDA in 2012. Based on the average annual minimum winter temperature over a 30-year period, the map divides the country into zones representing a spread of 10°F (zones 1-13), each subdivided into two half-zones with 5°F spreads (e.g., zone 1a and 1b).
This PHZM data set provides 1976-2005 mean extreme annual minimum temperature in grid and shapefile formats, at the following effective resolutions:
- 800 m (30 arc-seconds) for the conterminous United States (CONUS)
- 400 m (15 arc-seconds) for Hawaii and Puerto Rico
- 4 km (2.5 arc-minutes) for Alaska
Below are links to PHZM data in three formats. The shapefiles represent the half-zone classifications in a format suitable for mapping software. The grid files provide the average annual minimum winter temperature values on which the zones are based, giving the type of sub-zonal precision needed for scientific usage. There is also a listing of plant hardiness zones and half zones by ZIP code. Metadata describing the files is included with each format.
For an interactive map, to download cartographic images, or to read more about the maps, visit the USDA website: http://planthardiness.ars.usda.gov/PHZMWeb/Default.aspx
Under the terms of a Specific Cooperative Agreement between the US Department of Agriculture and Oregon State University (OSU), OSU retains ownership of the GIS datasets underlying the official 2012 USDA Plant Hardiness Zone Map. These datasets may be freely reproduced and redistributed, subject to the following conditions: (1) Both the USDA-ARS logo and OSU logo must be prominently displayed on any maps derived from the GIS datasets. (2) The data may not be altered in any way unless (a) there is an explicit and prominently displayed disclaimer that the map is not the official USDA Plant Hardiness Zone Map, and (b) the USDA-ARS and OSU logos are eliminated.