Frostline.info

Frost line depth in Washington

Estimated frost depth in typical soil runs from 10″ to 39″ across Washington's 39 counties. Pick your county or enter a ZIP code for a local estimate.

Deepest frost

  1. Okanogan County 39″
  2. Ferry County 38″
  3. Stevens County 36″
  4. Douglas County 35″
  5. Pend Oreille County 35″

Mildest

  1. Pacific County 10″
  2. Grays Harbor County 11″
  3. Wahkiakum County 12″
  4. Clallam County 12″
  5. King County 12″

Frost depth by county

CountyEst. frost (typical soil)Typical code range
Adams County32″30–42″
Asotin County29″24–36″
Benton County27″24–36″
Chelan County34″30–42″
Clallam County12″12–18″
Clark County14″12–18″
Columbia County25″24–36″
Cowlitz County13″12–18″
Douglas County35″30–48″
Ferry County38″30–48″
Franklin County29″24–36″
Garfield County27″24–36″
Grant County33″30–42″
Grays Harbor County11″12–18″
Island County13″12–18″
Jefferson County13″12–18″
King County12″12–18″
Kitsap County12″12–18″
Kittitas County32″30–42″
Klickitat County25″24–36″
Lewis County16″12–24″
Lincoln County34″30–42″
Mason County12″12–18″
Okanogan County39″30–48″
Pacific County10″12–18″
Pend Oreille County35″30–42″
Pierce County13″12–18″
San Juan County12″12–18″
Skagit County15″12–18″
Skamania County20″18–30″
Snohomish County13″12–18″
Spokane County33″30–42″
Stevens County36″30–48″
Thurston County13″12–18″
Wahkiakum County12″12–18″
Walla Walla County26″24–36″
Whatcom County17″18–24″
Whitman County32″30–42″
Yakima County30″24–42″

Common questions

What is the frost line depth in Washington?

It ranges from about 10 inches in the mildest county to 39 inches in the coldest, in typical soil.

Which Washington county has the deepest frost?

Okanogan County, at about 39 inches in typical soil.