Climate categories in viticulture

Large bodies of water, such as Lake Geneva in Switzerland, can have a moderating effect on the climate of a region.

Beyond establishing whether or not viticulture can even be sustained in an area, the climatic influences of a particular area goes a long way in influencing the type of grape varieties grown in a region and the type of viticultural practices that will be used.[7] The presence of adequate sun, heat and water are all vital to the healthy growth and development of grapevines during the growing season. Additionally, continuing research has shed more light on the influence of dormancy that occurs after harvest when the grapevine essentially shuts down and reserves its energy for the beginning of the next year's growing cycle.

In general, grapevines thrive in temperate climates which grant the vines long, warm periods during the crucial flowering, fruit set and ripening periods.[8] The physiological processes of a lot of grapevines begin when temperatures reach around 10 °C (50 °F). Below this temperature, the vines are usually in a period of dormancy. Drastically below this temperature, such as the freezing point of 0 °C (32 °F) the vines can be damaged by frost. When the average daily temperature is between 17 and 20 °C (63 and 68 °F) the vine will begin flowering. When temperatures rise up to 27 °C (80 °F) many of the vine's physiological processes are in full stride as grape clusters begin to ripen on the vine. One of the characteristics that differentiates the various climate categories from one another is the occurrence and length of time that these optimal temperatures appear during the growing season.[9]

In addition to temperature, the amount of rainfall (and the need for supplemental irrigation) is another defining characteristics. On average, a grapevine needs around 710 mm (28 in) of water for sustenance during the growing season, not all of which may be provided by natural rain fall. In Mediterranean and many continental climates, the climate during the growing season may be quite dry and require additional irrigation. In contrast, maritime climates often suffer the opposite extreme of having too much rainfall during the growing season which poses its own viticultural hazards.[9]

Other climate factors such as wind, humidity, atmospheric pressure, sunlight as well as diurnal temperature variations—which can define different climate categories—can also have pronounced influences on the viticulture of an area.[8][9]

Wine regions with Mediterranean climates.

Most California wine regions have a Mediterranean climate.

Penfolds winery, Magill Estate in South Australia.

Central Chilean wine regions experience a Mediterranean climate cooled in the summer by the Humboldt Current.

Stellenbosch wines from South Africa are from grapes grown in a Mediterranean climate.

Wine regions with Mediterranean climates are characterised by their long growing seasons of moderate to warm temperatures. Throughout the year there is little seasonal change, with temperatures in the winter generally warmer than those of maritime and continental climates. During the grapevine growing season, there is very little rainfall (with most precipitation occurring in the winter months) which increases the risk of the viticultural hazard of drought and may present the need for supplemental irrigation.[6]

The Mediterranean climate is most readily associated with the areas around the Mediterranean basin, where viticulture and winemaking first flourished on a large scale due to the influence of the Phoenicians, Greeks, and Romans of the ancient world.[6]

The Saxony wine region of eastern Germany is much more of a continental climate than the Rhine Valley, where most German wines are produced.

Hungary is removed from Atlantic and Mediterranean influences by distance and mountains, causing its wine regions to have a continental climate.

The Columbia Valley in Washington State and Oregon has a continental climate characterized by hot summers and moderately cold winters.

Although the climate is tempered somewhat by a Great Lake, it is continental in the Lake Michigan Shore AVA of SW Michigan.

The Upper Mississippi River Valley AVA in the Midwestern United States has a continental climate.

Xinjiang is NW China located near the centre of Asia, so its vineyards have a very continental climate.

Wine regions with continental climates are characterised by the very marked seasonal changes that occur throughout the growing season, with hot temperatures during the summer season and winters cold enough for periodic ice and snow. This is generally described as having a high degree of continentality. Regions with this type of climate are often found inland on continents without a significant body of water (such as an inland sea) that can moderate their temperatures. Often during the growing season continental climates will have wide diurnal temperature variations, with very warm temperatures during the day that drop drastically at night. During the winter and early spring months, frost and hail can be viticultural hazards. Depending on the particular macroclimate of the region, irrigation may be needed to supplement seasonal rainfall. These many climatic influences contribute to the wide vintage variation that is often typical of continental climates such as Burgundy.[6]

There are more wine regions with continental climates in the northern hemisphere than there are in the southern hemisphere. This is due, in part, to small land mass size of southern hemisphere continents relative to the large oceans nearby. This difference means that the oceans exert a more direct influence on the climate of the southern hemisphere wine regions (making them maritime or possibly Mediterranean) than they would on the larger northern hemisphere continents. There are also several wine regions (such as Spain) that have areas that exhibit a continental Mediterranean climate due to their altitude or distance from the sea. These regions will have more distinct seasonal change than Mediterranean climates, but still retain some characteristics like a long growing season that is very dry during the summer.[6]

The large Gironde Estuary, which feeds into the Atlantic Ocean, promotes a maritime climate in Bordeaux.

Wine regions of New Zealand adjacent to major cities. Its climate is maritime, which provides ample weather for wine-growing areas.

The Outer Lands wine regions of the Northeastern United States have a maritime climate.

Puget Sound is a major inlet promoting a maritime climate in its American Viticultural Area.

Port Phillip is an inland sea promoting a maritime climate in its surrounding wine regions, including the Melbourne metropolitan area.

The Garden Route wine regions of South Africa have a very mild subtropical maritime climate.

Hokkaido has a continental climate except on the coast of the Matsumae Peninsula where it is maritime.

Wine regions with maritime climates are characterised by their close proximity to large bodies of water (such as oceans, estuaries and inland seas) that moderate their temperatures. Maritime climates share many characteristics with both Mediterranean and continental climates and are often described as a "middle ground" between the two extremes.[10] Like Mediterranean climates, maritime climates have a long growing season, with water currents moderating the region's temperatures. However, Mediterranean climates are usually very dry during the growing season, and maritime climates are often subject to the viticultural hazards of excessive rain and humidity that may promote various grape diseases, such as mold and mildew. Like continental climates, maritime climates will have distinct seasonal changes, but they are usually not as drastic, with warm, rather than hot, summers and cool, rather than cold, winters.[6] Maritime climates also exist in some wine-growing areas of highlands of subtropical and tropical latitudes, including the southern Appalachian Mountains in the United States, the eastern Australian highlands and the central highlands of Mexico.

• Climate classification