Maritime climate
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Maritime_climate".

World map showing the oceanic climate zones.

An oceanic climate (also called marine west coast climate and maritime climate) is the climate typically found along the west coasts at the middle latitudes of all the world's continents, and in southeastern Australia. Oceanic climates are characterized by a narrower annual range of temperatures than are encountered in other places at a comparable latitude, and do not have the extremely dry summers of Mediterranean climates.

Similar climates, at least in thermal range, are also found in tropical highlands even at considerable distance from any coastline. Generally, they fall into Köppen climate classification Cfb or Cwb. The narrow range of temperatures results not from proximity to a coastline but instead to the slight thermal range of temperatures between seasons characteristic of tropical lowlands; altitudes are high enough that such places have at least one month cooler than 18 °C and do not qualify for grouping in the true tropical climates. Unlike the norm in true oceanic climates, these moist highland tropical climates may have a marked winter drought, as in Mexico City. As with oceanic climates, winters are relatively warm and summers are comparatively cool, so the agricultural potential in both oceanic climates and moist tropical highland climates is practically identical.

Precipitation

Precipitation is both adequate and reliable at all times of the year in oceanic climates, except in certain tropical highland areas, which would have tropical savanna or steppe climates (with a dry season in winter) if not for the high altitude making them cooler (Koppen Cwb). The Pacific Northwest and south-central Chile is often considered as having an Oceanic climate, although the dry summers in parts of this area actually fit the Mediterranean climate (Koppen "Csb").

Temperature

Overall temperature characteristics vary among oceanic climates; those at the lowest latitudes are subtropical from a thermal standpoint, but more commonly a mesothermal regime prevails, with cool, but not cold, winters and warm, but not hot, summers. Summers are also generally much cooler than in areas with a humid subtropical climate. Average temperature of warmest month must be less than 22 °C, and that of the coldest month warmer than -3 °C (Although American scientists prefer 0 °C in the coldest month). Poleward of the latter is a zone of subpolar oceanic climate (Köppen Cfc), with relatively mild winters (coldest month warmer than -3) and cool summers and a summer season (average temperature at least 10 °C or 50 °F) of less than four months; examples of this climate include parts of coastal Iceland in the Northern Hemisphere and extreme southern Chile in the Southern Hemisphere (the fact that this form of climate exists in both hemispheres ruling out the use of such terms as subarctic or boreal to denote it; even though these terms are used to refer to climates characterized by short summers, they are also synonyms for "northern" and therefore inappropriate).

Additional information

The British Isles experiences a typically maritime climate, with prevailing south-westerly winds from the Atlantic Ocean. The annual average temperature range in the UK is only about 10 °C. Although the west coast of Alaska experiences a maritime climate, the absence of an equally significant warm Pacific current in the upper-mid latitudes means that these regions are generally colder in winter, with more precipitation falling as snow.

All mid-latitude oceanic climates are classified as humid. Some rainshadow climates with thermal régimes similar to those of oceanic climates but steppe-like (BSk) or even desert-like (BWk) scarcity of precipitation include lowland valleys of Washington and Oregon to the east of the Cascade Range, Patagonia in southern Argentina, and the Atacama Desert in northern Chile. Another example are coastal areas in southeast Western Australia.

Countries/Regions with mild maritime climate

• Northern and southwest France
• The Netherlands
• Belgium
• Western Germany
• Western Switzerland (Lowland areas)
• Northwest Spain (often as csb)
• Northern Portugal (often as csb, too)
• Andorra
• Southwest Norway
• Parts of Denmark
• Ireland
• Great Britain
• New Zealand
• Tasmania, Australia
• Southern parts of Victoria and New South Wales, Australia
• Coastal areas of southwestern South Australia, Australia (as csb)
• Western areas of the south coast of Western Australia
• Central Argentina
• Southern and central Chile (as csb)
• Western parts of Oregon and Washington (U.S.A.) and British Columbia (Canada) (as csb; cfb in most of British Columbia)
• Northwest California (as csb) and the mildest coastal areas of the Alaskan panhandle (U.S.A.)
• Mountainous locations in some tropical countries (e.g. Indian subcontinent, Latin America, southern and central Africa; often as cwb)
• Parts of south and south-eastern South Africa
• Some mountainous areas across southern Europe
• Parts of Himalayas

The 0 °C (32 °F) isotherm (freeze line) or the -3 °C (26.6 °F) isotherms (persistent snow line) are the possible lines dividing the oceanic and the warm summer humid continental (Dfb) climates, in between which are the following regions:

• Eastern Germany
• Luxembourg
• Liechtenstein
• Western Poland
• Eastern Switzerland and parts of Austria
• Western Alps between 700 and 1000 meters.
• Central and Eastern Alps between 500 and 800 meters.
• Southern Sweden
• Fjord areas inland from the coast of southwest Norway and parts of the southeast coast of Norway
• Much of Denmark
• Southern coastal areas of the Alaskan Panhandle
• Most of the Czech Republic
• Parts of western Slovakia
• Northwest Romania
• Most of Hungary
• Slovenia
• Parts of Bosnia-Herzegovina
• Mountainous areas across southern Europe
• Himalayas
• Some southern coastal areas of New England

Notable cities with oceanic climates

Notable cities which have oceanic climates include:

Africa

• Port Elizabeth, South Africa
• Tristan da Cunha
• Addis Ababa, Ethiopia Cwb
• Nairobi, Kenya Cwb

Note that the latter two locations are high-altitude locations in the tropical areas that would be in savanna (Aw) or steppe (BSHw) zones except for high altitude.

Europe

• Amsterdam, Netherlands
• Bergen, Norway
• Berlin, Germany
• Bilbao, Spain
• Bordeaux, France
• Bratislava, Slovakia
• Brussels, Belgium
• Cardiff, Wales
• Copenhagen, Denmark
• Dublin, Ireland
• Geneva, Switzerland
• Glasgow, Scotland
• Gothenburg, Sweden
• Grenoble, France
• Hamburg, Germany
• London, England
• Ljubljana, Slovenia
• Paris, France
• Prague, Czech Republic
• San Sebastián, Spain
• Sarajevo, Bosnia and Herzegovina
• Vienna, Austria
• Vigo, Spain csb
• Wrocław, Poland

North America

• Mexico City, Mexico cwb
• Portland, Oregon, USA csb
• Prince Rupert, British Columbia, Canada
• Seattle, Washington, USA csb
• Vancouver, British Columbia, Canada
• Victoria, British Columbia, Canada csb

Central America

• Guatemala City, Guatemala cwb

Note that these locations have moist tropical highland climates.

South America

• Curitiba, Brazil
• Mar del Plata, Argentina
• Castro, Chile
• Puerto Montt, Chile
• Valdivia, Chile csb

The following have moist tropical highland climates:

• Bogotá, Colombia
• Quito, Ecuador
• Sucre, Bolivia cwb

Asia

• Thimphu, Bhutan cwb

Oceania

• Auckland, New Zealand
• Christchurch, New Zealand
• Dunedin, New Zealand
• Hobart, Australia
• Melbourne, Australia
• Sydney, Australia
• Wellington, New Zealand

Exceptions and borderline cases

Porto and San Francisco have a temperature range characteristic of an oceanic climate but so little rainfall during summer that they must be considered part of a Mediterranean climate zone, despite their milder summer temperatures.

Countries/Regions with subpolar oceanic climate

• Parts of coastal Iceland
• Faroe Islands
• Northwestern coastal areas of Norway reaching to 70°N on some islands
• Southern islands of Alaska and parts of the Alaskan Panhandle
• Far south of Chile and Argentina
• Parts of the Andes and Himalaya (as cwc)
• Mountainous areas of Europe, including highlands in Scotland, southwestern Norway

Some notable cities with the subpolar Cfc climate are:

• Harstad, Norway
• Thorshavn, Faroe Islands
• Unalaska, Alaska (also known as Dutch Harbor)
• Ushuaia, Tierra del Fuego, Argentina
• Vestmannaeyjar, Iceland
• La Paz, Bolivia cwc

Examples

Northern hemisphere

Southern hemisphere