Gardening in the cooler region of Northwestern U.S., USDA Plant Hardiness Zones ranging from 3a in Montana, through 9a the west coast of Oregon.
The USDA zones map is a useful system for determining what plants will survive and grow in certain areas of Northwestern U.S.
Understanding how these hardiness zones work means you can choose the right planting time, and optimize growing for your climate.
States in USDA Northwestern Plant Hardiness Map
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Idaho
Idaho’s climate varies widely influenced by the maritime weather characteristics. The USDA Plant Hardiness Zone classification ranges from 3b, to 7b near Boise.
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Montana
Montana is a state in the Mountain West subregion of the Western United States. The USDA Plant Hardiness Zone classification ranges from 3a, to 6a.
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Oregon
Most of Oregon has a generally mild climate, though there is significant variation given the variety of landscapes across the state. The USDA Plant Hardiness Zone classification ranges from 4b, to 9b near Eugene.
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Washington
Washington climate include the large semi-permanent high pressure and low pressure systems of the north Pacific Ocean. The USDA Plant Hardiness Zone classification ranges from 4a, to 9a near Olympia.
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Wyoming
Wyoming’s climate is generally semi-arid and continental. The USDA Plant Hardiness Zone classification ranges from 3a, to 6a.
Zones in USDA Northwestern Plant Hardiness Map
3a (-40 to -35 °F/-40 to -37.2 °C)
3b (-35 to -30 °F/-37.2 to -34.4 °C)
4a (-30 to -25 °F/-34.4 to -31.7 °C)
4b (-25 to -20 °F/-31.7 to -28.9 °C)
5a (-20 to -15 °F/-28.9 to -26.1 °C)
5b (-15 to -10 °F/-26.1 to -23.3 °C)
6a (-10 to -5 °F/-23.3 to -20.6 °C)
6b (-5 to 0 °F/-20.6 to -17.8 °C)
7a (0 to 5 °F/-17.8 to -15 °C)
7b (5 to 10 °F/-15 to -12.2 °C)
8a (10 to 15 °F/-12.2 to -9.4 °C)
8b (15 to 20 °F/-9.4 to -6.7 °C)
9a (20 to 25 °F/-6.7 to -3.9 °C)