The US Department of Agriculture publishes the Plant Hardiness Zone Map which is based on the minimum winter temperature. This is one factor in determining what plants to consider for yards or gardens.
Basis: average annual minimum winter temperature
Climate factors not considered:
(1) sunlight
(2) dryness/moisture
(3) summer heat
Range: -60°F to 70°F
Number of zones: 13 for 10 degree Fahrenheit ranges, with subzones "a" and "b" for 5 degree ranges
Temperature Range
Zone
-60°F to -55.1°F
1a
-55 to -50.1°F
1b
-50 to -45.1°F
2a
-45 to -40.1°F
2b
-40 to -35.1°F
3a
-35 to -30.1°F
3b
-30 to -25.1°F
4a
-25 to -20.1°F
4b
-20 to -15.1°F
5a
-15 to -10.1°F
5b
-10 to -5.1°F
6a
-5 to -0.1°F
6b
0 to 4.9°F
7a
5 to 9.9°F
7b
10 to 14.9°F
8a
15 to 19.9°F
8b
20 to 24.9°F
9a
25 to 29.9°F
9b
30 to 34.9°F
10a
35 to 39.9°F
10b
40 to 44.9°F
11a
45 to 49.9°F
11b
50 to 54.9°F
12a
55 to 59.9°F
12b
60 to 64.9°F
13a
65 to 70°F
13b
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