What Köppen climate classification is commonly given for San Francisco, California? The answer is Csb.
Csb is the Köppen code for San Francisco’s warm-summer Mediterranean climate. The C indicates a temperate climate, s means the summer is dry, and b means the warmest month averages below the threshold for a hot-summer Mediterranean climate. San Francisco therefore has cool, wet winters and mild, dry summers.
The city’s coastal setting explains much of this pattern. The cold California Current and Pacific Ocean moderate temperatures, while summer low pressure over California’s interior draws marine air through the Golden Gate. That airflow produces the city’s famous summer fog and cool winds.
A common mistake is choosing Csa, which is typical of hotter inland California locations with warmer summers. Cfa describes humid subtropical conditions and is not the usual classification for San Francisco. Local microclimates can vary sharply, but Csb is the standard citywide description.