Garden Resources » USDA Hardiness Zones » Southwest Hardiness Zone

Southwest Hardiness Zone Map

What Is the Map? What Is Your Zone?

The US Department of Agriculture produces a map for gardeners based on the average of low temperature readings taken from weather stations throughout the United States. The idea is to give the garden industry a way to communicate the cold hardiness of landscape plants. That is why the tag of a holly or any other landscape plant often says "hardy to zone __."

Of course, the map also provides vegetable and herb gardeners like you with a rough guide to the extent of cold where you live. Many of our perennial flowers and herbs are hardy as far north as zones 3 or 4. Cool season vegetables, most of which tolerate or even like a little frost, will grow well in Zones 7 and southward in the fall. This is roughly where we distribute transplants to your local garden center at the proper time for planting.

States in the Southwest Hardinss Zones:
Arizona, California, Nevada, Utah

Check the color of the section in your area of the map with the color key below.
Zones 5b through 10b represented here.

South-WestHardiness Zone Map Legend

 

Select Your Region


Garden Resources


USDA Hardiness Zones and Average Annual Minimum Temperature Range

  Zone  
  Fahrenheit  
    Celsius    
  Example Cities  
1
 Below -50 F  
Below -45.6 C
Fairbanks, Alaska;   Resolute, Northwest Territories (Canada) 
2a
-50 to -45 F  
-42.8 to -45.5 C
Prudhoe Bay, Alaska;   Flin Flon, Manitoba (Canada) 
2b
-45 to -40 F
-40.0 to -42.7 C
Unalakleet, Alaska;   Pinecreek, Minnesota 
3a
-40 to -35 F
-37.3 to -39.9 C
International Falls, Minnesota;   St. Michael, Alaska
3b
-35 to -30 F
-34.5 to -37.2 C
Tomahawk, Wisconsin;   Sidney, Montana
4a
-30 to -25 F
-31.7 to -34.4 C
Minneapolis/St.Paul, Minnesota;   Lewistown, Montana
4b
-25 to -20 F
-28.9 to -31.6 C
Northwood, Iowa; Nebraska
5a
-20 to -15 F
-26.2 to -28.8 C
Des Moines, Iowa;   Illinois
5b
-15 to -10 F
-23.4 to -26.1 C
Columbia, Missouri;   Mansfield, Pennsylvania
6a
-10 to -5 F
-20.6 to -23.3 C
St. Louis, Missouri; Lebanon, Pennsylvania
6b
-5 to 0 F  
-17.8 to -20.5 C
McMinnville, Tennessee;   Branson, Missouri 
7a
0 to 5 F
-15.0 to -17.7 C
Oklahoma City, Oklahoma;   South Boston, Virginia
7b
5 to 10 F
-12.3 to -14.9 C
Little Rock, Arkansas;   Griffin, Georgia
8a 
10 to 15 F
-9.5 to -12.2 C
Tifton, Georgia;   Dallas, Texas 
8b
15 to 20 F
-6.7 to -9.4 C
Austin, Texas;   Gainesville, Florida
9a
20 to 25 F
-3.9 to -6.6 C
Houston, Texas;   St. Augustine, Florida
9b
25 to 30 F
-1.2 to -3.8 C
Brownsville, Texas;   Fort Pierce, Florida
10a
30 to 35 F
1.6 to -1.1 C
Naples, Florida;   Victorville, California
10b
35 to 40 F
4.4 to 1.7 C
Miami, Florida;   Coral Gables, Florida
11
above 40 F
above 4.5 C
Honolulu, Hawaii;   Mazatlan, Mexico

Map Credits:
The 2003 US National Arboretum "Web Version" of the 1990 USDA Plant Hardiness Zone Map
USDA Miscellaneous Publication No. 1475. Issued January 1990.
Authored by Henry M. Cathey while Director, U.S. National Arboretum
Edited, formatted and prepared for the US National Arboretum web site by Ramon Jordan, March 1998 & Revised March 2001; January 2003
U.S. National Arboretum, Agricultural Research Service, U.S. Department of Agriculture, Washington, DC 20002

Note: This publication is not copyrighted, and permission to reproduce all or any part of it is not required.