What Köppen climate type dominates Western Europe? Cfb, the temperate oceanic climate. It is marked by mild winters, moderate summers, and precipitation spread fairly evenly through the year.
The Atlantic Ocean is the key influence. Prevailing westerly winds carry relatively mild, moist air inland, while the North Atlantic Drift helps keep winters warmer than those at similar latitudes in eastern Canada or Siberia. This maritime effect is especially strong in Ireland, the United Kingdom, western France, Belgium, the Netherlands, and coastal Norway.
Cfb does not describe every part of Western Europe. Mediterranean areas in southern Europe are commonly Csa or Csb, while higher elevations and more continental inland areas may shift into other classifications. The common mix-up is treating all of Europe as oceanic; the continent also includes Mediterranean, humid continental, subarctic, and arid zones.
In the Köppen system, Cfb means the warmest month averages below 22°C, at least four months average above 10°C, and there is no pronounced dry season.