Impacts of weather on wine

Napa Valley fog. | Courtesy Napa Valley Vintners

Ever wonder why Napa makes great Cabernet and Russian River makes great Pinot and California’s Central Valley does not? One of the main factors in creating fine wine is weather. Probably the most important weather component is temperature, because it changes during a single 24-hour period, called diurnal, and over growing seasons.

Another important factor is that different grape varieties thrive in different climates. For example, Pinot Noir produces much better wine fruit in cooler climates and as such thrives in Burgundy, France, as well as the cooler regions of Oregon and California. Cabernets and Merlots like the heat of Napa or Paso Robles.

Regardless of whether varietals work better in warmer or cooler climates, they all produce better wine grapes when the temperatures of a growing season rise and fall like a shallow bell curve — picture a hill peak as opposed to a mountain peak. Starting with spring, temperatures gently climb up to the hilltop and then gently back down for harvest. This allows for sugar and taste compounds to ripen while maintaining sufficient acids and other flavor/structure components.

Varietals produce better wine grapes when the temperatures of a growing season rise and fall like a shallow bell curve — picture a hill peak as opposed to a mountain peak.

Napa Valley makes great Cabernets largely because its best vineyards get quite hot. They also experience cool nights and mornings because of the cooling influence of San Pablo Bay and high mountain terrain. Sonoma Coast works for high quality Pinot Noir because of Pacific winds and fog.

Without treading the rocky road of climate change, let’s assume we believe in science and can see temperatures are certainly rising. If so, then how will that change the landscape of quality wine grapes?

We have already seen significant benefits in Washington’s Columbia Valley that until recently experienced hard winter freezes that would kill vineyards. Regions such as Germany’s Mosel and New York’s Finger Lakes were challenged to achieve sufficient ripeness in many years. Over the last 20 years, these regions have had a run of consistently riper vintages.

The coldest regions historically struggled to make quality wine because temperatures are borderline and regularly rapidly dropped before harvest inhibiting the ripening of flavor compounds. Because of this, places such as France’s Loire Valley, which had been known for red wines with off-putting green flavors, have produced richer, more balanced wines from their primary red — a Cabernet Franc — over the last several vintages. A good way to experience this is to try a Malbec from Argentina and a Malbec from the Cahors region of France.

Will Napa become a hot bed for Rhône grapes and Sonoma Coast start prioritizing Zinfandel and Grenache? Only time will tell. But one thing is for sure, these are some interesting times to be a wine lover.

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Lou Phillips
Lou is a Level 3 Sommelier based on the North Shore of Lake Tahoe, who loves traveling the wine world doing research for his writing. He also consults for collectors and businesses buying and selling fine wine and creating special events.