Mediterranean climate

A Mediterranean climate is a type of weather pattern found in many parts of the world. It is known for having dry, hot summers and wet, mild winters. This climate is named after the areas around the Mediterranean Sea, but it also occurs in other places such as California, Chile, parts of South Africa, and South Australia.

These climates usually appear on the western sides of continents, close to the ocean. The weather is influenced by large areas of high pressure that move during different seasons. Because of these conditions, plants like bushes and small trees grow well in these areas.

Regions with a Mediterranean climate are famous for growing certain crops, especially wheat, grapes, and olives. This has led to these places producing wonderful wines, oils, and breads that are enjoyed all over the world.

Köppen climate classification

Under the Köppen climate classification, "hot dry-summer" climates (classified as Csa) and "cool dry-summer" climates (classified as Csb) are often called "Mediterranean". The Köppen system uses letters to describe different climate types. The first letter shows the climate group, which for these areas is a temperate climate. Temperate climates have average temperatures above 0 °C (32 °F) but below 18 °C (64 °F) in their coldest months. The second letter shows the rain pattern, with "s" meaning dry summers. A dry summer month has less than 30 mm (1.2 in) of rain and falls between April and September in the north and October to March in the south. The third letter shows how hot the summers are: "a" means the warmest month is above 22 °C (72 °F), and "b" means it is below 22 °C (72 °F).

Dry-summer climates (Csa, Csb) are usually found on the west sides of continents. Csb zones include places like the Pacific Northwest, southern Chile, parts of west-central Argentina, parts of New Zealand, and parts of northwestern Spain (Galicia). Some high areas in warm parts of the world and several oceanic islands like Madeira, the Juan Fernández Islands, the western part of the Canary Islands, and the eastern part of the Azores also have these climates.

Under Trewartha's version of the Köppen system, a Cs climate needs at least eight months with average temperatures of 10 °C (50 °F) or higher and annual rain that does not exceed 900 mm (35 in), along with meeting Köppen's rain rules.

Precipitation

Chile has only four months of winter, and during that time, except when there is a quarter moon, it rains just one or two days. The rest of the days are so sunny that you don’t need a fire to stay warm. The summer is very mild, with pleasant breezes, so people can enjoy the sunshine all day long.

In summer, areas with a Mediterranean climate have clear skies and high temperatures because of strong, sinking air from a large area of high pressure over the oceans. This keeps the air very dry with almost no clouds. In places like coastal California, cold ocean currents help keep the air stable, which reduces the chance of rain but can create thick fog that usually disappears by midday.

During winter, the high pressure moves closer to the equator, allowing rainstorms to move into the area. Because of this, most of the rain in these regions falls during the winter and spring months. Summers can go four to six months with very little or no rain. In some places, like Southern Europe, rain is spread more evenly through the year, while in Southern California, summer is almost completely dry. The rain in these areas can be unpredictable, with some years having much more or less rain than others. For example, in Gibraltar, rain may start earlier than it does at the Dead Sea, and in Palestine, there is no rain at all during the summer, but early rains may arrive in autumn.

Temperature

Most places with a Mediterranean climate have gentle winters and very warm summers. But winter and summer temperatures can change a lot depending on where you are. For example, Funchal has mild winters with almost no frost or snow, while Tashkent can have cold winters with frost and snow. In summer, Seville gets very hot, but San Francisco has cooler summers because cold ocean water stays close by the shore.

Because these places are often near big bodies of water, their temperatures don’t change too much between winter and summer. Winter temperatures only sometimes drop below freezing, and snow is rare. Summer temperatures can range from cool to very hot, depending on how far you are from the water, how high up you are, and other factors. Strong winds from deserts can sometimes make summers very hot, which can increase the chance of wildfires. Some places, like Urfa and Erbil in Turkey and Iraq, get extremely hot in summer and cooler in winter because they are surrounded by deserts and mountains.

In higher areas, temperatures can be cooler in both summer and winter than in lower areas, sometimes too cool for some typical plants to grow. Some Spanish writers use the term ‘continental Mediterranean climate’ for these cooler areas, but the main climate classification doesn’t make this difference as long as winter temperatures stay above freezing.

Also, some high places next to tropical areas can have a Mediterranean-like climate with mild, wet winters and warm, dry summers. This can happen in places like Hawaii, where mountains block the rain.

Mediterranean biome

The Mediterranean forests, woodlands, and scrub biome is found in areas with a Mediterranean climate. This includes special kinds of plants and animals that have learned to live with dry summers and wet winters. You can find similar plants in nearby areas with different but close climates, like very wet or very dry places.

Plants in these areas have special ways to survive tough conditions. Many have small, tough leaves that help save water. They also grow in soils that don’t have a lot of nutrients. Some plants work together with tiny organisms in the soil to get the nutrients they need.

Water areas in these climates change a lot through the year. During rainy times, the water flow shapes the plants and animals. When it gets very dry, the plants and animals must be strong to survive. These water communities can bounce back after dry times, heavy rains, or fires. They are also feeling the effects of climate change.

Natural vegetation

Plants that grow naturally in Mediterranean climates must be able to handle long, hot, dry summers and wet winters. Examples include:

• Evergreen trees like casuarina, melaleuca, pine, and cypress
• Deciduous trees like sycamore and some types of oak
• Fruit trees like olive, figs, walnuts and grapes
• Shrubs like rosemary, Erica, Banksia, buckeyes, chamise, Bay laurel and some oaks
• Sub-shrubs like lavender, Halimium, grevillea and sagebrush
• Grasses like grassland types, Themeda triandra, bunchgrasses; sedges, and rushes
• Herbs like Achillea, Dietes, Helichrysum and Penstemon

Many of these natural plants have been removed to make space for farms. In places like the Sacramento Valley and Oxnard Plain in California, marshes and wetlands were drained to grow crops. In South Africa, areas that once had special plants called renosterveld are now mostly farms for wheat. However, in hilly and mountainous areas away from cities, many natural plants and animals still live undisturbed.

The fynbos plants in the southwest part of South Africa are famous for having many different kinds of flowers. They include plants from the Restionaceae, Ericas (Heaths) and Proteas families. Similar plants, like Banksias, grow in Australia. California also has many different native plants and garden varieties.

Hot-summer Mediterranean climate

This type of Mediterranean climate is the most common and is often called a "typical Mediterranean climate". Places with this climate have very warm summers, often with little rain. Winters are usually mild, but can sometimes feel cool or even chilly. Some cities in these areas might see snow during winter, while others never do.

You can find this climate around the Mediterranean Sea, southern Australia, southwestern South Africa, parts of Central Asia, northern areas of Iran and Iraq, the California Central Valley and Southern California, and Central Chile. In Southern California, the Channel Islands help keep the coast very warm in summer, but areas just a short distance inland can also feel very warm.

Warm-summer Mediterranean climate

This type of Mediterranean climate is called the warm-summer Mediterranean climate. It has warm, dry summers that are not very hot. The warmest month never gets above 22 °C (72 °F). The coldest month stays between 18 °C and about 0 °C (64 °F and 32 °F). There are also at least four months each year that stay above 10 °C (50 °F).

Cool ocean currents and higher latitudes often cause this cooler climate. Another reason is elevation. For example, Menton on the French coast has a different climate, but nearby Castellar, Alpes-Maritimes is higher up and has this cooler climate. The village of Siah Bisheh in Northern Iran also has this climate because it is in the Alborz mountains.

Winters in these areas are rainy and can be mild or a bit chilly. Some places may even have a little snow.

This climate is found in parts of northwestern Iberian Peninsula (like Galicia and the Norte region and the west coast of Portugal), coastal Northern California, the Pacific Northwest (western Washington, western Oregon and southern parts of Vancouver Island in British Columbia), central Chile, southern Australia and southwestern South Africa. It can also be found in some high, isolated areas of the Andes in Ecuador, Peru, Colombia and western Venezuela.

Cold-summer Mediterranean climate

The cold-summer version of the Mediterranean climate is rare and mainly found in high places along the west coasts of North and South America. This type has cool, dry summers, with fewer than four months where the average temperature reaches 10 °C (50 °F). Winters are also cool and wet, but no winter month drops below 0 °C (32 °F).

In North America, places with this climate are in the Olympic, Cascade, Klamath, and Sierra Nevada ranges in Washington, Oregon, and California. These areas are high up near places with warmer Mediterranean climates. A rare example in the tropics is at Haleakalā Summit in Hawaii.

In South America, this climate is found along the Andes in Chile and Argentina. The town of Balmaceda, Chile is one of the few confirmed places with this climate.

Small areas with this climate also exist at high elevations in Corsica.

In Norway, the village of Røstlandet in Røst Municipality, above the Arctic Circle, has temperatures that are unusually warm for its location north of 67°N.