How Good and Bad Weather Affect Your Wine

Weather Vintages Illustration
Illustration by Alyssa Nassner

Champagne lovers hail  2002  as one of the best Champagne vintages in a century but say 2012 was a horrible vintage for Bordeaux yet an excellent year in Champagne. What does this mean exactly? 

 It all comes down to weather.   

The Wine & Spirit Education Trust (WSET) defines weather as “the annual variation that happens relative to the climatic average.” This differs from its definition of climate, which is “the annual pattern of temperature, sunlight, and rainfall averaged out over several years.” The climate doesn’t change from year to year, but the weather can. Make sense?

Vines are perennial plants whose life cycle is consistent. Vine dormancy and pruning occur in the winter—December through March in the Northern Hemisphere, and July through September in the Southern Hemisphere.

Budburst, when the first leaf tissue of the vine appears, is the next stage, and happens between March and May in the north or September and November in the south. Then, around May and June or November and December, fruit set and flowering set in. After that, the onset of veraison or ripening, the most important stage in the process, commences so that between July and September or January and March, the harvest can take place.   

But various climatic influences can affect the way grapes taste at harvest time.   

“We associate higher quality vintages with ones in which the vines are able to achieve a natural balance with the given conditions,” says John Hamel, managing director of winegrowing for Hamel Family Wines. “For us, with the goal of dry farming, we see this balance in vintages where we receive ample rainfall and cool temperatures throughout the winter period, and a gradual, gentle accumulation of heat and light throughout the course of the season.” 

He goes on to say that “winter, any excess of rain, cold temperatures or dry extreme heat at any point in the season has the potential to disrupt the vine’s natural cycle of vegetative growth to fruit development and ultimate maturation… [which] can be the difference between a great, good, and bad vintage.”    

Grapevines need nutrients, sunlight and water to survive, so imagine how their health can suffer when they’re deprived of one or all of these essential lifelines. They need to be tended to lovingly and caringly during their formative months, from the time they start as buds to when they become fully grown and ripe, harvest-ready grapes.   

For example, in that stellar  2002  Champagne vintage, the entire growing season was just about perfect. Spring was mild with no inclement weather to speak of, with a warm summer, and into fall before harvest, dry and warm days. Those conditions allowed for even ripening, which resulted in optimal levels of sugars, acid and tannins.

However, sometimes things don’t go as planned. Winter freeze can linger and give the buds a late start, shortening the already truncated ripening period.

That’s what happened in 2012 in Bordeaux. After that wet freeze, rain saturated the vines and created conditions for fungal growth. Vineyard managers had to contend with mildew, which can eliminate grapes’ flavors or make them taste moldy.

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If that weren’t enough, the heat wreaked further havoc when it spiked around harvest time, which had already been delayed due to the uneven development of grapes and frenetic weather.

You remember photosynthesis from science class, right? It occurs when energy from sunlight converts to chemical energy to fuel plants’ metabolic activities. Well, at 95°F and above, the rate of photosynthesis dramatically decreases, and will eventually shut down, causing heat stress. That’s bad news for plants, and it was bad news in Bordeaux since many of those summer days were well into the 100s. 

Most grapes need near-perfect conditions to thrive. That doesn’t mean that the weather has to be warm year-round with little precipitation or inclement weather. What it does mean is that whatever the region’s weather, it is consistent and appropriate for the respective grapes’ growth.   

Some winemakers, however, take a more optimistic approach to defining good and bad vintages.   

“There are neither good nor bad vintages, per se,” says Michael Silacci, head winemaker for Opus One Winery. “A good vintage is a reflection of a winemaker’s ability to stay focused and read the whims of Mother Nature well enough to make a classic wine that expresses time and place.” 

Published on March 9, 2021
Topics: Wine Basics