Köppen climate classification
The Köppen climate classification divides climates into five main climate groups, with each group being divided based on seasonal precipitation and temperature patterns. The five main groups are "A" (tropical), "B" (dry), "C" (temperate), "D" (continental), and "E" (polar). Each group and subgroup is represented by a letter. All climates are assigned a main group (the first letter). All climates except for those in the "E" group are assigned a seasonal precipitation subgroup (the second letter). For example, "Af" indicates a tropical rainforest climate. The system assigns a temperature subgroup for all groups other than those in the "A" group, indicated by the third letter for climates in "B", "C", and "D", and the second letter for climates in "E". For example, "Cfb" indicates an oceanic climate with warm summers as indicated by the ending "b". Climates are classified based on specific criteria unique to each climate type.
Climate categories in viticulture
In viticulture, the climates of wine regions are categorised based on the overall characteristics of the area's climate during the growing season. While variations in macroclimate are acknowledged, the climates of most wine regions are categorised (somewhat loosely based on the Köppen climate classification) as being part of a Mediterranean (for example Tuscany), maritime (ex: Bordeaux) or continental climate (ex: Columbia Valley). The majority of the world's premium wine production takes place in one of these three climate categories in locations between the 30th parallel and 50th parallel in both the northern and southern hemisphere. While viticulture does exist in some tropical climates, most notably Brazil, the amount of quality wine production in those areas is so small that the climate effect has not been as extensively studied as other categories.