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.
Desert climate
There are two variations of a desert climate: a hot desert climate ("BWh"), and a cold desert climate ("BWk"). Furthermore, to delineate "hot desert climates" from "cold desert climates", there are three widely used isotherms: either a mean annual temperature of 18 °C (which is the most accurate and most commonly used), or a mean temperature of 0 °C or −3 °C in the coldest month, so that a location with a "BW" type climate with the appropriate temperature above whichever isotherm is being used is classified as "hot arid" (BWh), and a location with the appropriate temperature below the given isotherm is classified as "cold arid".