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An oceanic climate, also known as a marine climate, is the temperate climate sub-type in Köppen classification represented as Cfb, typical of west coasts in higher middle latitudes of continents, generally featuring cool summers and mild winters (for their latitude), with a relatively narrow annual temperature range and few extremes of temperature. Oceanic climates can be found in both hemispheres generally between 40 and 60 degrees latitude, with subpolar versions extending to 70 degrees latitude in some coastal areas. Other varieties of climates usually classified together with these include subtropical highland climates, represented as Cwb or Cfb, and subpolar oceanic or cold subtropical highland climates, represented as Cfc or Cwc. Subtropical highland climates occur in some mountainous parts of the subtropics or tropics, some of which have monsoon influence, while their cold variants and subpolar oceanic climates occur near polar or tundra regions.

Precipitation

Locations with oceanic climates tend to feature frequent cloudy conditions with precipitation, low hanging clouds, and frequent fronts and storms. Thunderstorms are normally few, since strong daytime heating and hot and cold air masses meet infrequently in the regions, but are more common in subtropical highland climates where these air masses meet more frequently due to the influence of hotter weather in the subtropics or tropics, especially in monsoon-influenced climates. In most areas with an oceanic climate, precipitation comes in the form of rain for the majority of the year. Most oceanic climate zones, however, experience at least one snowfall per year. Snowfall is more frequent and commonplace in the subpolar oceanic climates due to the colder weather in those locations.

Temperature

Overall temperature characteristics of the oceanic climates feature cool temperatures and infrequent extremes of temperature. In the Köppen climate classification, oceanic climates have a mean temperature of 0 °C (32 °F) or higher (or −3 °C (27 °F) or higher) in the coldest month, compared to continental climates where the coldest month has a mean temperature of below 0 °C (32 °F) (or −3 °C (27 °F)) in the coldest month. Summers are warm but not hot, with the warmest month having a mean temperature below 22 °C (72 °F). Poleward of the latter is a subtype of it and is the subpolar oceanic climate (Köppen Cfc),^[1] with long but relatively mild (for their latitude) winters and cool and short summers (average temperatures of at least 10 °C (50 °F) for one to three months). Examples of this climate include parts of coastal Iceland, the coast of Norway north of Bodø, the Scottish Highlands, the mountains of Vancouver Island, and Haida Gwaii in Canada, in the Northern Hemisphere and extreme southern Chile in the Southern Hemisphere (examples include Punta Arenas), the Tasmanian Central Highlands, and parts of New Zealand.

Cause

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Oceanic climates are not necessarily found in coastal locations on the aforementioned parallels; however, in most cases oceanic climates parallel higher middle latitude oceans.^{[clarification needed]} The polar jet stream, which moves in a west to east direction across the middle latitudes, advances low pressure systems, storms, and fronts. In coastal areas of the higher middle latitudes (45–60° latitude), the prevailing onshore flow creates the basic structure of most oceanic climates. Oceanic climates are a product and reflection of the cool ocean adjacent to them. In the autumn, winter, and early spring, when the polar jet stream is most active, the frequent passing of marine weather systems creates the frequent fog, cloudy skies, and light drizzle often associated with oceanic climates. They are typically found poleward of Mediterranean climates, except in Australia where they are poleward of both such climates and humid subtropical climates due to the shape of the continent. Only in Europe do they penetrate far inland, where they eventually transition into warm-summer humid continental climates; in other continents, they are blocked by a large mountain range or limited by nearby oceans.

The North Atlantic Gulf Stream, a tropical oceanic current that passes north of the Caribbean and up the East Coast of the United States to North Carolina, then heads east-northeast to the Grand Banks of Newfoundland, is thought to greatly modify the climate of northwest Europe.^[2] As a result of the North Atlantic Current, west coast areas located in high latitudes like Ireland, the UK, and Norway have much milder winters (for their latitude) than would otherwise be the case. The lowland attributes of western Europe also help drive marine air masses into continental areas, enabling cities such as Dresden, Prague, and Vienna to have maritime climates in spite of being located well inland from the ocean.

Locations

Europe

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Oceanic climates in Europe occupy a large stretch of land, from Norway's Atlantic coast and the British Isles, southeast to some parts of Turkey.

Western Europe is almost exclusively oceanic between 45°N to 55°N; including most of France (away from the Mediterranean), nearly all of Belgium, the Netherlands, Austria, most of Luxembourg, most of Denmark, western Germany, northwestern Switzerland, south coast and western areas of Norway north to Skrova and extreme southern Sweden.

While most of Southern Europe is climatically Mediterranean, some parts of Southern Europe also have oceanic climates. However, these instances of the climate are highly variable, and often somewhat anomalous. The north coast of Spain, the western Azores off the coast of Portugal are too wet in summer to be Mediterranean, and too mild in summer to be humid subtropical, though they often have winter means above 9 °C (48 °F), unusual for European oceanic climates.

Another anomalous case can be found in northwestern Turkey, including northern Istanbul. These places are, in a strict air-mass sense, not oceanic: they are affected by southerlies directly from the Mediterranean, and polar intrusions from Siberia.^[4] Yet their position near the Black Sea makes them too wet in summer to be Mediterranean, too mild during winter to be humid continental, and not hot enough in summer to be humid subtropical; therefore Köppen classifies them as oceanic. Despite their anomalous position, however, their temperatures, around 4–5 °C (39–41 °F) in winter and 20–22 °C (68–72 °F) in summer, are not wholly atypical for European oceanic climates.

Some Eastern European regions such as the north of Croatia and Serbia and some parts of the Czech Republic, also have oceanic climates; these are generally near the boundary for being humid continental.

The line between oceanic and continental climates in Europe runs in a generally north to south direction. For example, western Germany is more impacted by milder Atlantic air masses than eastern Germany. Thus, winters across Europe become colder to the east, and (in some locations) summers become hotter. The line between oceanic Europe and Mediterranean Europe normally runs west to east and is related to changes in precipitation patterns and differences to seasonal temperatures; although intrusions of polar air, remnants of marine air-masses, and higher summer precipitation can create oceanic climates in Eastern Europe and transcontinental regions as far south as 40°N.^{[citation needed]}

The Americas

The oceanic climate exists in an arc spreading across the northwestern coast of North America from the Alaskan panhandle to northern Washington. In addition, some east coast areas such as Block Island, Cape Cod, Martha's Vineyard, and Nantucket have a similar climate.^[5] An extensive area of oceanic climates distinguishes the coastal regions of southern Chile and extends into bordering Argentina.

Africa

The only noteworthy area of maritime climate at or near sea-level within Africa is in South Africa from Mossel Bay on the Western Cape coast to Plettenberg Bay (the Garden Route), with additional pockets of this climate inland of the Eastern Cape and KwaZulu-Natal coast. It is usually warm most of the year with no pronounced rainy season, but slightly more rain in autumn and spring. The Tristan da Cunha archipelago in the South Atlantic also has an oceanic climate.

Asia and Oceania