For the first time this spring I woke up to fog this morning – not clouds – fog. I thought of all the lovely people visiting Napa Valley waking up, looking out the window of their hotel, and feeling a little bummed. I could just hear them saying “Darn! It’s going to be cloudy and cold today! Is it going to rain?”
I wished I could somehow tell them all not to despair. But, at least their disappointment was short-lived. By the time they had breakfast and hopped in the car for their 10:00 winery appointment things were already starting to break up. They thought “Maybe things are looking up.” By 10:30, or so, we had full sun.
And, I was thinking “Yay! We’re moving into our summer weather pattern!” It’s made up of mostly cool, foggy nights and bright, sunny days. Very comfortable for the visitors and the vines.
Why am I prattling on about this? Because, when it comes to climate, the fog is really the key reason Napa Valley is a famous winegrowing region. Without San Pablo Bay, down there at the southern end of the valley, it would be too hot, here, to grow good wine. The warm days encourage maturation. The foggy nights keep the progress kind of leisurely and the cool temperatures also keep the acidity bright.
Here’s the deal: Every winegrowing region in the world wants the same thing. They want enough heat and light to get the grapes ripe – and not too much more. And, no rain at harvest time.
Every region has its gripes. Here in the Napa Valley, the last three vintages not withstanding, we worry about too much heat and sun. It’s a relatively nice problem, because at least we get a crop, but too much heat brings the grape sugar up faster than the flavors mature. It’s not a tragedy when this happens but the winemaker has to make a decision: Either make a high-alcohol wine (the most common reaction; the sugar supplies the alcohol) or harvest at the “normal” sugar and make a lack-luster vintage. Heat cooks off the acidity, too. Low-acid wines aren’t as refreshing or lively – not to mention food friendly – as those with the right level (even reds are enlivened by a good, solid acidity).
Digression: In California, it’s perfectly legal to add acid, but the best winemakers would rather harvest it. Acid adjustments don’t always integrate well and might leave a kind of aspirin-like aftertaste. That said, acid additions are quite common.
In Bordeaux or Burgundy they worry about the opposite: They’re afraid that they won’t get enough sun and heat during the growing season, plus rain at harvest isn’t all that uncommon. So, potential rot problems aside, they may not get enough sugar and the acid may be painfully high. In most cool-climate situations, it’s legal to add sugar (the term for adding sugar is “Chaptalization” – for French chemist, Jean-Antoine Chaptal (1756-1832.) Deacidification is quite another issue and is only legal in a relative handful of regions.
The past three vintages here in sunny Napa Valley haven’t been so sunny. We’ve had three uncharacteristically cool “Bordeaux Vintages” in a row, complete with unwelcome rainfall during harvest. We’re all hoping it was just a temporary blip – that climate change isn’t cooling us down. We’ll see…
So, around here, fog is a beautiful thing! As long as it lifts. Cheers!
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