Heat units in Northwest vineyards as much as 29% ahead of last year

By on August 9, 2021
Pacific Northwest precipitation departure from normal through July 2021. (Images from WestWide Drought Tracker, Western Region Climate Center; University of Idaho)

By the time climate researcher Greg Jones issues his next Weather and Climate Summary and Forecast near Labor Day, harvest for sparkling wine in the Pacific Northwest will have begun.

That doesn’t include the estate plantings for Abacela Winery, where Jones recently took over as chief executive officer, but the Albariño at his family’s iconic Fault Line Vineyards in Oregon’s Umpqua Valley American Viticultural Area won’t be far off.

“The overall summer forecast continues to tilt the odds to warmer than average temperatures and remaining seasonally dry for the western U.S.,” Jones reported the day after the annual Albariño Days celebration at Abacela while continuing to work on his ClimateOfWine.com.

Vineyard managers and winemakers have the experience, knowledge and resources to deal with the grapes ripening under those temperatures. However, the domino effect surrounding the drought can bring irrigation problems for some and another season of smoke from wildfires.

“Sorry for the broken record, but the western U.S. continues to be dominated by drought conditions,” he wrote. “Currently over 99% of the west is in some level of drought. The highest drought categories, extreme and exceptional, now make up roughly 65% of the western U.S.”

And there’s no expectation that it will change until the start of fall. 

“Both short- and long-term drought indicators along with the seasonal outlook point to the western U.S. being highly likely to continue dry conditions into the start of the fall,” Jones noted.

His latest overview of growing degree days, drought reports and weather forecasts indicates that the 2021 vintage in the Pacific Northwest is leaning more toward the historically hot 2015 growing season than last year. It’s a different story throughout much of California wine country because of the influence of marine layers. 

“Most inland areas continue running 5-20 days ahead of normal growing degree-day accumulations, while the coastal zones in central to southern California are near average to seven days behind,” Jones wrote.

Another factor for Northwest vineyards is that wine grape vines will shut down as a result of heat stress, so during the recent “heat dome” episode, those lofty temperatures added to the GDD totals but did not necessarily help with ripening. In a number of varieties, shut down begins around 95 degrees, but that does not apply to all grapes.

For the record, in 2015 the Jones family began bringing in its award-winning Albariño on Sept. 14. That heat didn’t stop winemaker Andrew Wenzl’s Albariño from earning a gold medal — and better — at four West Coast competitions the following year. Last year, harvest for the white grape native to Galicia commenced Sept. 29 at Fault Line Vineyards.

Parts of Idaho rival Red Mountain in heat units

Sydney Weitz-Nederend and her family continue to invest in Scoria Vineyard, a young planting near the Snake River on the outskirts of Caldwell, Idaho. Weather data indicates Scoria ranks among the warmest sites in the Pacific Northwest. Nederend and her husband, James, also own and operate award-winning Koenig Vineyards. (Photo by Eric Degerman/Great Northwest Wine)

In terms of growing degree days, the comparison of 2021 to 2015 still applies, and the GDD remain well above the 2020 vintage. The outlook for wine country from Northern California to Washington remains likely to finish with slightly above-average temperatures.

“As we head into the home stretch for the last few months of the 2021 vintage, growing degree-days for four locations that I have tracked for many years in wine regions in Oregon are all substantially above the 1981-2010 normals through July (28-43%) and above the average of the last 16 years for the sites (16-22%),” Jones wrote. “Compared to the 2015 vintage, one of the warmest years on record in Oregon, Medford is now above the 2015 vintage while Roseburg and McMinnville are now within a percent or two of 2015, and Milton-Freewater is roughly 8% below the GDD accumulated during the 2015 vintage.

“The four locations are currently 9 to 29% above the 2020 vintage at this point,” he added.

By the end of July, the McMinnville recording station Jones monitors accrued 1,501 GDD. In 2015, it stood at 1,574. This year at Abacela near Roseburg, there were 1,907 GDD to start August. Six years ago, it read 1,991.

In the Rogue Valley city of Medford, it is still 2021 that’s ahead of 2015 with 2,226 GDD vs. 2,190. In the Walla Walla Valley town of Milton-Freewater, Ore., the current vintage stood more moderate at 2,135 GDD. In 2015, there were nearly 200 more GDD (2,317).

Washington State University’s AgWeatherNet charts growing degree days at 177 stations across the state as well as parts of Oregon and Idaho.

Among the warmest in Washington is the Benton City station near Red Mountain, where were 2,357 GDD were recorded through July 31. A year ago, it read 1,941 GDD. In 2015, there were an identical 2,357 GDD.

Not far off is the Wahluke Slope. There were 2,221 growing degree days recorded at the East Mattawa station. A year ago, it charted 1,804 GDD. During the 2015 vintage, it stood at 2,222 when August began.

At Phinny Hill Vineyard in Klickitat County’s Horse Heaven Hills, that station measured 2,017 GDD. In 2020, it read 1,688. Back in 2015, before the temperatures really began to race in the Columbia Valley, there were 2,074 heat units.

The North Sunnyside station in the Yakima Valley collected 1,962 GDD. A year ago, the accumulation stood at 1,671 GDD. During the blistering 2015 season, it was 2,049.

Along the Columbia Gorge, Husum notched 1,454 GDD. A year ago, it stood at 1,146. The Pullman school’s station in Woodinville collected 1,181 GDD, compared with 987 GDD last year. Back in 2015, it received 1,338.

This year, a number of vineyards in Idaho’s Snake River Valley became integrated into AgWeatherNet. Canyon County northwest of Boise includes with young Scoria Vineyard on the Sunnyslope at 2,343 — just behind the Red Mountain site — Rose Cottage near vaunted Fraser Vineyard (2,307) and historic Sawtooth Vineyard, which had achieved 2,279 GDD. Ada County is represented by young Dude DeWalt at 2,241 and 3 Horse Ranch in the Eagle Foothills AVA with 2,159.

In the bi-state Lewis-Clark Valley AVA, Umiker Estate Vineyard at Clearwater Canyon Cellars in Lewiston, Idaho, reported 2,274 growing degree days.

About Eric Degerman

Eric Degerman is the President and CEO of Great Northwest Wine. He is a journalist with more than 30 years of daily newspaper experience and has been writing about wine since 1998. He co-founded Wine Press Northwest magazine with Andy Perdue and served as its managing editor for a decade. He is a frequent wine judge at international wine competitions throughout North America and orchestrates 10 Northwest competitions each year.


  1. Yamhill Vineyards says:

    I would like to see a website that publishes GGD on a continues basis made available to the wine industry

  2. Eric Awes says:

    So sorry to read the spike in heat units for the three state AVA’S. It’s hard to Fathom what I saw for the Puget Sound and the Olympic mountain range areas.

  3. Greg jones says:

    Well done as always Eric …

    • CEO,
      Thank you again for sharing your expertise with the industry, helping us to better understand what’s happening to our climate and how it can affect winegrowers and consumers.

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