Grapevines Need Temperate Climates
- Vines need long, warm periods during crucial flowering, fruit set and ripening periods
- After harvest, vines need to go dormant over the winter, so they can regenerate and marshal their nutrients for the next season
- Too cold a winter is not good, however, because freezing can actually kill the vines
- Vinifera vines may die if the temperature falls below about 5°F
- Some vinifera vines, like Cabernet Franc, can withstand colder winters
- Many North American varieties are hardier and can withstand even lower temperatures
Most productive wine growing regions are situated between 30 degrees and 50 degrees latitude, either north or south of the equator.
Within these temperate zones, three primary types of climates affect wine grape production.
- Hot temperatures during the summer and winters cold enough for ice and snow.
- During the growing season, wide day/night temperature swings.
- Frost and hail problems.
- Vintage variation due to weather.
- Examples – Burgundy, Rioja, north Italy, Mendoza Argentina, Loire Valley, Finger Lakes, Texas High Plains, Columbia Valley of Washington/Oregon
- Long moderate to warm growing seasons
- Little seasonal change – temperatures in winter are warmer than in maritime or continental climates.
- During growing season, little rainfall. Drought an issue, irrigation may be needed
- Examples – California, Tuscany, Southern Rhône, Provence, Languedoc, Catalonia, South Australia, Western Australia, Chile Central Valley
- Close proximity to large bodies of water that moderate their temperatures.
- Often excessive rain and humidity may promote grape diseases, such as mold and mildew
- Distinct seasonal changes, but with warm, rather than hot, summers and cool, not cold, winters.
- Examples – Bordeaux, Willamette Valley Oregon, Rias Baixas Spain, New Zealand, Southern Chile, Alsace, Southern Oregon
It is often handy to classify climates as either warm or cool.
Warm Climate Classification
- Consistent temperatures throughout the season.
- The slow drop off from summer into fall gives grapes ample opportunity to become fully ripe but more natural acidity in the grapes is lost.
- Inland California, Argentina, Australia, Southern Italy, Greek Islands, Central and Southern Spain, Central and Southern Portugal, most of South Africa, Southern France, Southern Italy
Cool Climate Classification
- Cool climate regions get just as hot as warm climates in the peak of the season.
- However, temperatures drop off quickly towards harvest, which makes the wines taste different. Lower temperatures preserve acidity but they also make it difficult for grapes to ripen.
- Coastal California, Northern France, Washington State, Oregon, New York, Southern Chile, Northern Italy, New Zealand, Germany, Western Cape South Africa
Some Other Climate Terms
- Macroclimate – the climate of a broad area – Dry Creek Valley in Sonoma, Pomerol in Bordeaux, Asti in Italy
- Mesoclimate – the climate of a particular vineyard site
- Microclimate – the specific environment in a small restricted space-such as a row of vines
The term “microclimate” is often misused to refer to a vineyard site or even a small wine region.
Vines Need Water
- On average, a grapevine needs around 710 mm (28 in) of water during growing season.
- The Mediterranean and continental climates may be quite dry and require additional irrigation.
- Maritime climates often have too much rainfall during the growing season.
Bodies of Water
Bodies of water affect climate and hence wine producing conditions in many ways. The proximity of wine producing regions to bodies of water is a major theme in wine geography.
In a cold climate region like the New York Finger Lakes, the lakes store summer heat during the day and release it to warm up cooler evenings.
In the warm climate region of California’s Lake County, warm air from land rises in the afternoon and is replaced by cooler air from the lake, which cools the land.
Major ocean currents are also responsible for cooling coastal lands, which otherwise would be too hot for viticulture. The Cape Region of South Africa would be too hot but for the Benguela Current that brings in cool water from the Antarctic. The Humboldt Current in the Pacific does the same thing for Chile. The California Current swoops down from Alaska, cooling the entire Pacific Coast of North America from British Columbia down to Baja California in Mexico.
Cooling fog is an important phenomenon. In Monterey County, California, fog from Monterey Bay pushes in and down the Salinas Valley, bringing cool climate conditions to appellations like the Santa Lucia Highlands.
Rivers have long been wine producing areas. Rivers tend to retain the sun’s heat and reflect it out or up to warm adjacent vineyard areas that would otherwise be too cold.
With global warming, established wine producing regions become hotter. The risk is that the grapes will become too sweet. The yeast used in winemaking converts grape sugars into alcohol, but beyond a certain level the alcohol will kill the yeast and stop fermentation, leaving unfermented sugar. You risk too much sugar, too much alcohol, or both.
Sooner or later, what were once cool climate regions become too hot, forcing growers to change the grapes they grow, which is a problem in Europe’s highly traditional winegrowing regions. Cool climate viticulture will inexorably move to higher latitudes, north in the northern hemisphere and south in the southern. In the northern hemisphere, there is plenty of land to the north available to colonize. England, as one example, is benefiting. In the southern hemisphere, Chile and Argentina have breathing space to the south, but Australia and South Africa do not.
Diurnal (Day/Night) Temperature Variation
This is an important factor as the wine grower gauges ripening vs. acid retention. Wine grapes start off with high acidity and no sugar. As the grapes ripen, sugar increases as acidity decreases, and flavors develop. Ideally, vines will enjoy warmth and sunshine during the day, allowing them to develop their sugars and flavors through the ripening process, and then benefit from cool nights to prevent the grape from respiring too much of the valuable acidity and flavor compounds. In an ideal scenario, sugars will increase to just the right amount necessary to ferment the juice into a wine of appropriate alcohol content, acidity will decrease to a level that gives the juice a satisfying acidic pucker without burning the mouth, and flavor compounds will be optimal—all at the same time. This is the ideal time to harvest, providing that it does not rain during harvest, and factoring in the availability of labor.
We have already discussed cooling ocean fogs, but there are other factors that cool off vineyard nights.
High altitude vineyards absorb more solar radiation during the day and then cool off rapidly at night to maintain acidity. This allows the vineyards of Salta in Argentine, at 8000 feet above sea level, the world’s highest, to produce wines even though, at 25 degrees south, the region is outside of the usual 30-50 degree temperate zone. The same phenomenon favors Israel’s Golan Heights vineyards, 4000 feet in elevation.
High latitude growing areas have longer ripening days and the yet greater temperature drops at night. The vineyards in Washington State, for example, see summer ripening days that are two hours longer than those of Napa or Sonoma in more southerly California. A problem in higher latitudes, of course, is that winter can be so cold that the vines die, an ongoing issue in Washington State.
Arid wine regions have temperature drops at night due to lack of warming humidity. Again, interior Washington State, as in Walla Walla, is an example.
Because high diurnal temperature swings are absent in the vast Central Valley of California, it is known for low quality, bulk production of wine grapes, as well as table and raisin grapes (not to mention a veritable cornucopia of other kinds of produce that do well in warm climates). In the center of the valley, the northward running San Joaquin River and the southward running Sacramento River converge into an inland delta system that significantly cools evenings, resulting in productive fine wine regions like Clarkesville and Lodi. West of this area, the Sierra Foothills counties benefit both from the higher altitude and from the effect of these cooling river systems.
Weather and Wine
- Weather in spring shapes quantity of harvest because of presence or absence of spring frosts, and their intensity
- Weather at the end of summer is crucial to quality since this is the major ripening period
- Choice – harvest sooner (no rains yet) or wait for the absolute best conditions and get higher quality grapes (if labor available)
- Winemakers use commercial weather services to monitor weather conditions both at the macro and micro level: using weather satellites for a larger picture and vineyard-specific sensors
- Planting a vineyard on or near the highest point on any given location will promote better air and water drainage.
- Air drainage is essential in frost and freeze events. Cold air is heavier than warm air, so it settles in low areas.
- Water drainage is also important because standing water will limit the oxygen available to the vine root system.
Vineyard Aspect – angle toward the sun
- In the northern hemisphere, in cool climates, southern, southeastern, and southwestern slopes allow maximum heat accumulation to grow and ripen grapes.
- In climates with warm or hot summers and cold winters, eastern, northern, and northeastern slopes moderate the heat.
- The reverse is true in the southern hemisphere.
- Ideal soil is deep, well-drained, with some water-holding capacity (so vines don’t suffer in heat).
- Grapevines like infertile ground. Roots spread far and deep in search of water and nutrients.
- Reflective and re-radiation effects of the soil are important in cooler growing regions where every heat unit is needed to ripen the grapes.
- Growing season – the number of days between last frost (28°F) in spring and the first frost in fall.
- The season must be long enough to let both the fruit (grapes) and vegetative parts (leaves) of the vine mature.
- Look for the coolest possible site that can fully ripen any variety on a consistent basis.