- How ripe the grape can get
- How long the grape can stay on the vine before harvest
- The amount of alcohol in the wine
Think about a basket of fruit and the way the fruit changes flavor as it ripens. Green vs. yellow bananas or hard vs. soft peaches. The sugars that come through during ripening make the fruit sweeter. That's obvious, yes?
Well, the same is true for fruit that ripens on the vine. The longer you keep grapes on the vine, the riper they get. You'll pick up on this when you're tasting wine. It won't take long before you're able to note how ripe the fruit was when harvested. Whereas ripened grapes leave you with a sweet, lush flavor, unripe fruit often leaves you with a tartness. Overripe grapes (from hot climates) tend to leave you with petrol and high alcohol (or, "heat"). Obviously, the amount of time winegrowers can leave their grapes on the vine is determined by the climate and when first frost comes.
Knowing what we know now, you can start to imagine that wines from warmer climates (California, South Africa, Australia, etc.) are bound to be richer, deeper, and fuller tasting. Wines from cooler climates (New York, Germany, France, etc.) receive cooler sun while on-vine (and are therefore not as ripened when picked). In cold climates (Niagara) they might be picked earlier, too. These wines are often lighter, crisper, more tart, and do not age as well. An added caveat is that wines from hot climate have more alcohol content because part of the ripening process in hot sun results in higher levels of alcohol in the grape once fermented.
One last point to make: between warm and cold climates, there is a middle, "temperate" ground. New York's Finger Lakes Region, where mild climates can last through October harvests, produce delicious, but tart, wines is a prime example. That's because it was never really hot enough for long enough to produce the richer, riper grapes, even though the growing seasons are as long as they are in warm climates (think first frost in October).
When it comes to vintages (the harvest year), sometimes a particular region has a warmer climate. This was the case in 2009 in the Finger Lakes. People were talking about that year being a "good year" in the Finger Lakes. That's because the rieslings from that year benefitted from the extra warmth the season brought. They are much fuller, and lusher, than in a typical year.
In essence, that's what climate does to our wine. So, go out and experiment. Try a South African Shiraz and compare it to a French Syrah. Or a Chardonnay from California vs. one from Virginia.