Washington climate

Washington Plant Hardiness Zones

Washington’s towns run from zone 6a to zone 9b: the average coldest winter night is 27.8°F at Neah Bay and -8.9°F at Twisp.

Hardiness zones in Washington

In USDA’s colors, neighboring states washed out. Zones follow elevation, coasts and cities down to half a mile. Drawn by WeatherOverTime from the USDA-ARS and Oregon State University PRISM Climate Group 2023 GIS data; this is not the official USDA Plant Hardiness Zone Map.

Map of the 2023 plant hardiness zones across Washington, from zone 5a to zone 9b, with the state’s border drawn.
  • 5a
  • 5b
  • 6a
  • 6b
  • 7a
  • 7b
  • 8a
  • 8b
  • 9a
  • 9b

Open the live map with plant hardiness zones

Towns by zone

Each town’s 1991-2020 average annual extreme minimum at its center, read from the map’s 800 m grid. Warmest zone first.

9b Zone 9b, 25 to 30°F 1 towns

9a Zone 9a, 20 to 25°F 100 towns

8b Zone 8b, 15 to 20°F 232 towns

8a Zone 8a, 10 to 15°F 16 towns

7b Zone 7b, 5 to 10°F 30 towns

7a Zone 7a, 0 to 5°F 77 towns

6b Zone 6b, -5 to 0°F 19 towns

6a Zone 6a, -10 to -5°F 8 towns

Counties

At the county’s center; a county with hills or a coast spans several zones.

CountyZone at the centerAverage coldest night
Adams County7a1°F
Asotin County7a2°F
Benton County7b5.6°F
Chelan County7a0.1°F
Clallam County8b15.3°F
Clark County8b15.8°F
Columbia County7a4.2°F
Cowlitz County8b16.4°F
Douglas County6b-2.5°F
Ferry County6a-6.1°F
Franklin County7a3.5°F
Garfield County7a3.3°F
Grant County7a0.4°F
Grays Harbor County8b18.4°F
Island County8b17.6°F
Jefferson County7b7.3°F
King County8b15.2°F
Kitsap County9a20°F
Kittitas County7a1.7°F
Klickitat County7a2°F
Lewis County8b15.6°F
Lincoln County6b-3.6°F
Mason County8b15.6°F
Okanogan County6a-9.2°F
Pacific County8a13.4°F
Pend Oreille County6a-7.9°F
Pierce County8b15.8°F
San Juan County9a20.8°F
Skagit County8b15.1°F
Skamania County8a11.4°F
Snohomish County8a13.3°F
Spokane County6b-1.3°F
Stevens County6b-4.5°F
Thurston County8a14.1°F
Wahkiakum County8b17°F
Walla Walla County7a4.3°F
Whatcom County7b5.8°F
Whitman County7a1.1°F
Yakima County7a2.6°F

The zones

A plant hardiness zone is set by the average of each winter’s single coldest temperature, 1991 to 2020: zones are 10°F apart and each half zone, a and b, 5°F. It says how cold a winter night usually gets, not the coldest it has ever been, and nothing about summer heat, rain or soil. Plant labels give the coldest zone a perennial survives in.

ZoneAverage coldest nightIn Celsius
6a-10 to -5°F-23.3 to -20.6°C
6b-5 to 0°F-20.6 to -17.8°C
7a0 to 5°F-17.8 to -15.0°C
7b5 to 10°F-15.0 to -12.2°C
8a10 to 15°F-12.2 to -9.4°C
8b15 to 20°F-9.4 to -6.7°C
9a20 to 25°F-6.7 to -3.9°C
9b25 to 30°F-3.9 to -1.1°C

Sources

Hardiness zones: USDA Plant Hardiness Zone Map, 2023, Agricultural Research Service, U.S. Department of Agriculture, from the GIS data of the PRISM Climate Group, Oregon State University, which may be freely reproduced and redistributed. Drawn by WeatherOverTime from the USDA-ARS and Oregon State University PRISM Climate Group 2023 GIS data; this is not the official USDA Plant Hardiness Zone Map.