Sun in a Shadow, Climate of the Yakima Valley AV

The federal government designated this appellation in early 1983; but the area has been cultivating wine grapes as well as a cornucopia of apples, cherries, pears, and apricots for multiple generations. Such agricultural bounty reflects a remarkable climate. The Yakima Valley enjoys 300 days of sunshine each year, including more summer sun than even San Diego, Phoenix, or Honolulu. That’s a big surprise to people who associate Washington State with rain. But the snowcapped volcanoes of the Cascade Mountains dramatically influence the weather in this corner of the country. Skies that are cloudy in Seattle turn clear by the time you reach the Yakima Valley, only about two hours’ drive to the east. Climate scientists call this phenomenon a “rain shadow.”

Rainshadow Effect

Most of Washington State’s weather comes off the Pacific Ocean. The vibrant green landscapes along the coast and around the Puget Sound are the direct result of these very moist west-to-east atmospheric currents. And when those masses of moving air hit the Cascades, they are forced to rise and cool rapidly. Such a quick shift releases huge amounts of mountain precipitation – more than 80 inches a year or doubles the amount that falls on Seattle. So by the time those clouds reach eastern Washington State, they have nothing left to give. They dissipate, and the skies over the Yakima Valley are left clear and sunny. The region gets only 7 to 8 inches of precipitation each year, and the definition of a true desert is anything less than 10.

Yakima Valley High Desert Region

How do wine grapes grow in a desert? The answer is irrigation. Yakima Valley’s wine industry captures pure mountain snowmelt from the Cascades as it flows into regional river systems and vast natural aquifers. The water is then applied to vineyards with scientific accuracy. Soil moisture levels and vine canopy conditions are closely monitored to ensure that irrigation water is applied to achieve optimum grape ripeness. Too much water has an adverse effect on wine quality, and it also represents poor stewardship of a precious environmental resource. So Yakima Valley growers steer clear of both.

Drip irrigation applied directly to the vine

Abundant sunshine and clean water are crucial to world-class wine grape cultivation. But they are not sufficient. Seasonal temperature totals or what scientists call heat accumulation are equally vital to thriving vines; and this is where the Yakima Valley really shines. On the wine region classification system developed by the University of California at Davis, the Yakima Valley’s 2,600 to 3,000 “growing-degree (F) days” define this AVA

as “Region II” and place it on par with the Bordeaux wine region of France. Even better is the way this heat accumulates. If it were uniformly warm all season long, Yakima Valley’s grapes would lose their natural acidity and the resulting wines would be flabby. However, there is a dramatic difference between day and night temperatures in this valley during the growing season: afternoon highs in the 80s (F) plunge down to the 50s (F) after midnight. It’s what climate scientists call a significant diurnal shift; and those dramatic temperature swings enable grapes to retain their natural, flavor-enhancing acids. Regions that lack such ideal conditions can “fix” the quality of the grapes that they harvest—through chemical additions or other manipulations in the winery—but it’s never quite like Mother Nature’s own touch.

Average rainfall

So what does all this mean to the wines of the Yakima Valley? In a word: balance. The climate of this region combines sunshine and water as well as heat and cold like almost nowhere else on earth. The end result is grapes that are ripe and yet crisp; and those become wines that are lush and yet fresh. Most remarkable is the way this balance is achieved across multiple varieties—from Riesling and Chardonnay to Syrah, Merlot, and Cabernet. When people ask which grapes grow well in the Yakima Valley, the best response might be which grapes don’t grow well here. Such diversity is a marketing challenge in a world where wine regions prefer to hang their hat on a single style; but it’s also a delight to wine consumers with open minds and open palates.

Content reference: “Mean Number of Clear Days” from the Western Regional Climate Center -&- “Washington Observed Climate Normals (1971-2000)” from the Department of Atmospheric Sciences at the University of Washington.