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Plant hardiness zones relate to average winter minimum temperatures, and were originally developed by the United States Department of Agriculture (USDA). Plant types are often categorized according to hardiness zones which describe the geographical regions in which they can survive.
Zones are categorized according to the mean of the lowest temperature recorded each winter, termed the "average annual minimum temperature".
North America
The map below shows USDA zones throughout North America. An equivalent European Zone Map is also available.
Orignal Source: U.S. Dept. Agriculture
See also: Hardiness Zone - Wikipedia.
USDA Zones in Celsius
The map, above, gives zone temperatures in Fahrenheit, but you can use the table below to convert to Celsius.
Zone 1 : Below -46°C (-50°F)
Zone 2 : -46°C to -40°C (-50°F to -40°F)
Zone 3 : -40°C to -34°C (-40°F to -30°F)
Zone 4 : -34°C to -29°C (-30°F to -20°F)
Zone 5 : -29°C to -23°C (-20°F to -10°F)
Zone 6 : -23°C to -18°C (-10°F to 0°F)
Zone 7 : -18°C to -12°C (0°F to +10°F)
Zone 8 : -12°C to -7°C (+10°F to +20°F)
Zone 9 : -7°C to -1°C (+20°F to +30°F)
Zone 10 : -1°C to +4°C (+30°F to +40°F)
Zone 11 : Above +4°C (+40°F)
USDA Zones for US Cities
|
City
|
Zone
|
City
|
Zone
|
|
Albuquerque, New Mexico
|
7
|
Oklahoma City, Oklahoma
|
7
|
|
Anchorage, Alaska
|
4
|
Omaha, Nebraska
|
5
|
|
Atlanta, Georgia
|
7-8
|
Orlando, Florida
|
10
|
|
Baltimore, Maryland
|
7-8
|
Philadelphia, Pennsylvania
|
7
|
|
Boston, Massachusetts
|
6-7
|
Phoenix, Arizona
|
9
|
|
Burlington, Vermont
|
4
|
Pittsburgh, Pennsylvania
|
6
|
|
Chicago, Illinois
|
5-6
|
Portland, Maine
|
5-6
|
|
Cincinnati, Ohio
|
7
|
Portland, Oregon
|
9
|
|
Dallas, Texas
|
8
|
Raleigh, North Carolina
|
8
|
|
Denver, Colorado
|
5-6
|
St. Louis, Missouri
|
7
|
|
Detroit, Michigan
|
5-6
|
Salt Lake City, Utah
|
7
|
|
Honolulu, Hawaii
|
11
|
San Antonio, Texas
|
9
|
|
Houston, Texas
|
9
|
San Diego, California
|
10
|
|
Las Vegas, Nevada
|
9
|
San Francisco, California
|
10
|
|
Los Angeles, California
|
10
|
Seattle, Washington
|
8
|
|
Memphis, Tennessee
|
8
|
Tampa, Florida
|
9-10
|
|
Miami, Florida
|
11
|
Tucson, Arizona
|
8
|
|
Minneapolis, Minnesota
|
5
|
Tulsa, Oklahoma
|
7
|
|
Nashville, Tennessee
|
7
|
Washington, D.C.
|
7-8
|
|
New Orleans, Louisiana
|
9
|
Wichita, Kansas
|
6
|
|
New York, New York
|
7
|
Wilmington, Delaware
|
7-8
|
|
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