For the lover of quality wines, vintage year — the year during which grapes are grown and harvested and the year printed on a wine label — is of extreme importance. The reason is simple: the same wine produced by the same vineyard and by the same winemaker can vary significantly in quality and taste from growing season to growing season, year to year. The most crucial factor for this variability is weather. In an ideal climate, wine grapes will have just enough sun, just enough coolness, just enough aridity, and just enough rain to allow the fruit to ripen slowly, from bud break in the spring to maturity in the early autumn, developing from small green berries to mature grapes bursting with ripe, concentrated flavors and balanced levels of fruit, residual sugar, and acidity — the very definition of "a good year".
But climates — especially areas of micro-climates like the Bordeaux region of France — are rarely ideal. Excessive rains can rot grapevines, delay the harvest, or upset the natural balance of sugar and acidity. Too much exposure to sunlight can increase sweetness and alcohol levels to unpalatable levels, and frost, hail and wind can kill vines altogether, resulting in poor yields. Vintage years with poor weather can produce wines that are thin or green or excessively jammy or tannic. In addition to these troubles, vintners also have to combat the onslaughts of insect infestation, mildew, fungi and microbial infections which can wreak havoc on the harvest. Granted, modern winemaking techniques can overcome some of these pitfalls, but ultimately you can’t fool Mother Nature. Despite all the winemaker’s considerable skill, the wine is still made in the vineyard.
In the United States, a vintage wine must contain at least 85 percent of the varietal grape labeled on the bottle; if the wine is designated as particular to an American Viticultural Area such as Napa Valley, then this percentage is increased to 95. Non-vintage wines (labeled NV), such as sparkling wines, some Ports and sherries, are wines blended from different harvest years to achieve a consistent style.