Mediterranean climate
A
Mediterranean climate is one that resembles those of the lands bordering the
Mediterranean Sea. These climates occur on the western coasts of continental landmasses, roughly between the latitudes of 30° and 45° north and south of the equator.
Besides the
Mediterranean Basin, the regions having a Mediterranean climate include much of
California and small parts of the adjacent
Pacific Northwest, the
Western Cape in South Africa, central
Chile, the coastal areas of southern
Western Australia and western
South Australia.
The northernmost example of a Mediterranean climate occurs on the southeastern tip of
Vancouver Island,
Canada, which receives less precipitation than nearby cities such as
Vancouver and
Seattle, Washington owing to its proximity to the Olympic Mountain rain shadow. Oak
savannas and sclerophyllous vegetation attest to the unusual climate of the region.
Some of the valley
microclimates of western Washington and Oregon may have climates similar to the Mediterranean type. These regions have mild winters and dry summers, but tend to receive very heavy precipitation during the rainy season.
During summer, regions of Mediterranean climate are dominated by subtropical high pressure cells, and are thus equivalent to
deserts from the point of view of air mass positions, while during winter the
polar front brings weather conditions similar to those of an
oceanic climate, with frequent precipitation. As a result, areas with this climate receive almost all of their yearly
rainfall during the
winter season, and may go anywhere from 2-5 months during the
summer without having any significant precipitation.
As an example,
San Francisco in
California,
USA, receives an average of 448 mm (17.6 in.) of rain from November through April each year, but averages only 52 mm (2 in.) of rain for the rest of the year, and receives almost no precipitation at all during the months of July and August.
All regions with Mediterranean climates have relatively mild winters, but summer temperatures are variable depending on the region. For instance,
Athens,
Greece experiences rather high temperatures in the summer, while San Francisco, California has cool, mild summers due to its proximity to the Pacific Ocean. Because all regions with a Mediterranean climate are near large bodies of water,
temperatures are generally moderate with a comparatively small range of temperatures between the winter low and summer high (although the daily range of temperatures during the summer is large, except along the immediate coasts). Temperatures during winter rarely reach freezing (except in areas with a high elevation), and
snow is almost never encountered. In the summer, the temperatures range from mild to very warm, depending on distance from the open ocean, elevation, and latitude. Even in the warmest locations with a Mediterranean-type climate, however, temperatures don't reach the high levels of
desert regions.
Inland locations sheltered from or distant from sea breezes can experience severe heat during the summer. Locations inside the
Sacramento Valley of northern California, for example, are subject to summer temperatures characteristic of hot deserts (often around 40 °C or 100 °F), although winters are rainy enough to allow lusher vegetation than is typical in deserts. In
Perth, Australia hot, dry summers (100 F) and cool, wet winters (65 F) are a perfect example of a Mediterranean climate. Unlike the coastal climates that are designated
Csb in the
Köppen climate classification—characteristic of places with cooler summers—the hotter, typically inland areas have the
Csa classification that indicates a hot summer. Areas that experience the typical Mediterranean pattern of cool, rainy winters and very dry summers, but which experience milder average summer temperatures include,
Porto, in
Portugal and
San Francisco, in
California.
Likewise, locations that are slightly higher latitude and cut off from milder ocean winds may have somewhat colder winters and more distinct seasons. This "temperate Mediterranean" climate is most noticeable in northern Italy and Greece, as well as southern Oregon. In these areas, plants that are commonly associated with milder Mediterranean climates, such as
citrus,
date palm,
olive,
oleander and
eucalyptus, can be frozen to death in the occasional severe winter.
Areas of high altitude adjacent to locations with Mediterranean climates may have the cold winters that are characteristic of a
continental climate; under Köppen's scheme such places might earn the designation
Dsa,
Dsb or even
Dsc.
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Explanation of Mediterranean Climate
