Which climate zone has a coldest month average above 18°C?

A climate zone with a coldest-month average above 18°C is classified as Tropical in the Köppen system. The defining feature is consistently high temperature: every month averages at least about 18°C, separating tropical climates from temperate and continental ones.

Köppen’s classification, developed by climatologist Wladimir Köppen and later refined by Rudolf Geiger, uses long-term temperature and precipitation patterns. Tropical climates are labeled Group A and are divided into rainforest (Af), monsoon (Am), and savanna (Aw or As) climates according to rainfall seasonality.

A common mix-up is confusing the tropical temperature threshold with the boundaries of the subtropical zone. Subtropical climates may have very hot summers, but their coldest month falls below the tropical threshold. The rainfall pattern then determines which tropical subtype applies.