Washington wineries benefit from grapes ripening with about two more hours of  summer sunlight each day than in California wine regions.  Gradually cooling Autumn temperatures in  Washington also help wine grapes reach full maturity, while maintaining desirable acid levels.  A  variety of climates and soils combine with the long summer sunlight hours of northern latitudes to create prime growing regions,  predominantly in the valleys and on the hillsides of areas east of the Cascade Mountain range.

Climates of individual Washington wine regions differ dramatically.  Cross cut north to south by the  Cascade Mountains, Washington State is more mild and lush to the west of this volcanically formed  barrier than the lands to its east.  In fact, 98% of the state's wine grapes are grown on the east side of  the Cascades where five of Washington's official AVA/Appellations are located.  The arid climate and conditions of eastern Washington permit grapes to fully ripen, while developing complex fruit flavors, pleasing aromatics and nuances.  A few Washington wineries grow vineyards  on the cooler, western side of the Cascades, where occasional marine breezes drift over the ridges of the Coast Range into the Puget Sound wine region, moderating temperatures and increasing rainfall.

All totaled, Washington wine regions produce more wine grapes than any other state in the U.S.,  except California. Wine grapes are now the fourth most important fruit crop in Washington State  behind apples, cherries and pears.