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Average Date of Last Killing Frost
Most planting and seed sowing instructions are based on the average last frost date, which is defined as "the last day in the spring that you might have a killing frost".
When making your plant selections, it is wise to consult more experienced gardening friends and neighbors for advice regarding possible local micro-climates or unusual conditions. Their knowledge can be invaluable.
 
Temperature Conversion Table
|
Temperature ranges of Plant Hardiness and Gardening Zones
|
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
|
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The Garden Helper is a free gardening encyclopedia and guides to growing and caring for gardens, plants and flowers. Helping gardeners grow their dreams since 1997.
