Marine west coast

Köppen climate classification is one of the most widely used climate classification systems. It was first published by Russian German climatologist Wladimir Köppen in 1884, with several later modifications by Köppen, notably in 1918 and 1936. Later, German climatologist Rudolf Geiger (1954, 1961) collaborated with Köppen on changes to the classification system, which is thus sometimes called the Köppen–Geiger climate classification system.

The Köppen climate classification system has been further modified, within the Trewartha climate classification system in the middle 1960s (revised in 1980). The Trewartha system sought to create a more refined middle latitude climate zone, which was one of the criticisms of the Köppen system (the C climate group was too broad).

The Köppen climate classification scheme divides climates into five main climate groups: A (tropical), B (dry), C (temperate), D (continental), and E (polar). The second letter indicates the seasonal precipitation type, while the third letter indicates the level of heat.

Group A: Tropical (megathermal) climates

This type of climate has every month of the year with an average temperature of 18 °C (64.4 °F) or higher, with significant precipitation.

Group B: Dry (arid and semiarid) climates

This type of climate is defined by little precipitation.

Multiply the average annual temperature in Celsius by 20, then add

If the annual precipitation is less than 50% of this threshold, the classification is BW (arid: desert climate); if it is in the range of 50%–100% of the threshold, the classification is BS (semi-arid: steppe climate).

A third letter can be included to indicate temperature. Originally, h signified low-latitude climate (average annual temperature above 18 °C (64.4 °F)) while k signified middle-latitude climate (average annual temperature below 18 °C), but the more common practice today, especially in the United States, is to use h to mean the coldest month has an average temperature above 0 °C (32 °F), with k denoting that at least one month's averages below 0 °C.

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Wikipedia