In Köppen climate classification, what does the third letter 'c' indicate?

In Köppen climate classification, the third letter “c” indicates a cool summer. It applies when only one to three months have average temperatures above 10°C, making the warm season noticeably brief.

The third letter describes summer heat in C and D climates. “a” means hot summer, with the warmest month averaging above 22°C; “b” means warm summer, with at least four months above 10°C but the warmest month below 22°C; and “c” marks the coolest of these summer categories.

A common mix-up is confusing the third letter with the second. In a code such as Cfc, the second letter “f” means there is no dry season, while the final “c” describes the limited summer warmth. The first letter C identifies a temperate climate.

Wladimir Köppen first published his climate classification in 1884, and Rudolf Geiger later helped develop the Köppen–Geiger version. The system uses temperature and precipitation patterns to connect climate zones with natural vegetation.