USDA Plant Hardiness Zones & Average Annual Extreme Minimum Temperature (1977-2005)
Table and information from http://planthardiness.ars.usda.gov/PHZMWeb/
| Zone | Fahrenheit | Example Cities |
|---|---|---|
| 1a | −60 to -55 °F | |
| 1b | -55 to -50 °F | Fairbanks, Alaska; Resolute, Northwest Territories (Canada) |
| 2a | -50 to -45 °F | Prudhoe Bay, Alaska; Flin Flon, Manitoba (Canada) |
| 2b | -45 to -40 °F | Unalakleet, Alaska; Pinecreek, Minnesota |
| 3a | -40 to -35 °F | International Falls, Minnesota; St. Michael, Alaska |
| 3b | -35 to -30 °F | Tomahawk, Wisconsin; Sidney, Montana |
| 4a | -30 to -25 °F | Minneapolis/St.Paul, Minnesota; Lewistown, Montana |
| 4b | -25 to -20 °F | Northwood, Iowa; Nebraska |
| 5a | -20 to -15 °F | Des Moines, Iowa; Illinois |
| 5b | -15 to -10 °F | Columbia, Missouri; Mansfield, Pennsylvania |
| 6a | -10 to -5 °F | St. Louis, Missouri; Lebanon, Pennsylvania |
| 6b | -5 to 0 °F | McMinnville, Tennessee; Branson, Missouri |
| 7a | 0 to 5 °F | Oklahoma City, Oklahoma; South Boston, Virginia |
| 7b | 5 to 10 °F | Little Rock, Arkansas; Griffin, Georgia |
| 8a | 10 to 15 °F | Tifton, Georgia; Dallas, Texas |
| 8b | 15 to 20 °F | Austin, Texas; Gainesville, Florida |
| 9a | 20 to 25 °F | Houston, Texas; St. Augustine, Florida |
| 9b | 25 to 30 °F | Brownsville, Texas; Fort Pierce, Florida |
| 10a | 30 to 35 °F | Naples, Florida; Victorville, California |
| 10b | 35 to 40 °F | Miami, Florida; Coral Gables, Florida |
| 11a | 40 to 45 °F | Honolulu, Hawaii; Mazatlan, Mexico |
| 11b | 45 to 50 °F | |
| 12a | 50 to 55 °F | |
| 12b | 55 to 60 °F | |
| 13 | 60 to 65 °F | |
| 13b | 65 to 70°F |