I recently had a friend return from doing some wine tasting in Napa. While he said he enjoyed the wine, he did complain that it was windy and cold. And, he said he was told that the wind helped the wine. So, he asked me "How does wind affect a wine?"
Luckily, I had recently been doing some reading, and this exact situation was described. It turns out that it's not just the wind, it a cool wind that helps. And, as is true with many of the premiere wine growing regions, Napa is helped by the cool afternoon breezes that come in off the ocean. These cool winds actually cause the leaves in the vineyard to close-down their tiny pores (stoma). Without going any further into plant botany, this slows down the ripening process during the growing season. And, slower ripening results in grape skins that are thicker along with smaller berries (i.e., grapes) and smaller bunches. This produces concentrated flavors and, in red grapes, a bit more tannin. It can also help with increased acidity. All good stuff for making wine.
So, when you visit wine county and feel the cool afternoon breezes, don't complain. They are helping to make the wine even better. Cheers!