The climate Diagram, according to Heinrich Walter, is one of the most practical and simple tools for comparing climates worldwide. From these diagrams you can see the overall average temperature and precipitation, plus their seasonal patterns with respect to one another. They also give an idea of the duration of cold/warm or wet/dry seasons and the extent of their fluctuations.

Also, by comparing climate diagrams for two different geographic areas, you can roughly estimate whether plants originating from one region will do well in another. Of course, there are many parameters that come into play here, but, all things being equal, it is the distribution of precipitation through the seasons which makes the important difference.

The climate diagram for Volos shows a long arid period (pink), from May till about mid September, during which there is significant water deficit, and a humid period (blue), from October till about May, during which there is water surplus. This type of wet-winter, dry-summer climate, is typical Mediterranean.

The Climate Classification System used here, which consists of a three-letter code, was first introduced by the Russian-German climatologist Wladimir Koeppen in 1900 and is the most widely used classification system today.

The Koeppen classification code consists of one capital letter, followed by two lower case letters:

• The first letter - which can take values A, B, C, D and E - represents one of the 5 major climatic types recognized by Koeppen, based on annual and monthly averages of temperatures and precipitation.
• The second letter - which can take values f, m, s and w - designates subgroups with specific seasonal characteristics of temperature and precipitation.
• The third letter - which can take values a, b, c, d, h and k - denotes further variations in climate.

Based on the Climate Diagram above, we can easily conclude that the appropriate Climate Classification Code for Volos is:

Csa

where:

C:	Denotes a humid mid-latitude climate, with warm, dry summers and cool, wet winters.
s:	Indicates there is a dry season in the summer of the respective hemisphere.
a:	Suggests hot summers, where the warmest month is over 22oC. These conditions can only be found in C and D climates.

The Mediterranean climate is a special type of climate that describes a regime of hot summer drought and winter rain.

Regions of Mediterranean-type climate are small and far apart from one another, making up less than 2% of the world's land area.

As can be seen by the map below, they occur roughly between 30^o and 45^o N and S latitude, on the west coasts of continents, where there are offshore cold ocean currents.

Major regional expressions of Mediterranean climate include:

• The Mediterranean proper, the only large area where the summer-dry pattern prevails, hence the climate's name. It incorporates coastal zones bordering the Mediterranean Sea, including Southern Europe, much of Northern Africa and Asia Minor, and extends all the way to the Iranian Highlands;
• Central and Southern California;
• Central Chile;
• The Capetown area of South Africa;
• Southwestern Australia.

However, there could, very well, be other regions with similar climates. H.Roemer, for example, in his excellent essay entitled "Plants From Old-World Winter-Rain Climates Suitable for Rock Gardens in Victoria, BC" maintains that the distribution of precipitation in British Columbia, as well as in the entire area between Comox - Vancouver - Seattle - Portland, is very similar to that of Tripolis, Greece, and the Mediterranean realm in general, although average temperatures in Victoria tend to be somewhat lower.

Mediterranean plants have adapted to the extreme difference in rainfall and temperature between winter and summer in several ways:

• Plants grow most vigorously in early spring, when days become longer and the soil is moist, then go into a period of relevant dormancy during the summer. A second season of plant growth follows the autumn rains.
• Most shrubs and trees are evergreen and have small, leathery leaves (sclerophyllus), with thick cuticles, to combat water loss. In fact, leaves are frequently so reduced, as to appear needle-like.
• Annuals complete their life cycle by setting seed before dying during the summer. Seeds survive the dry season and sprout after the autumn and winter rains. Bulbous plants lose their foliage in summer but have stored enough food and moisture in their underground organs to survive the arid period and send up new shoots during the rainy seasons.

Many typical members of the shrub flora are aromatic and contain highly flammable oils and resins, which promote fire, especially during the arid summer months. Thus, adaptation or pre-adaptation to fire is important among various plant taxa. For example:

• many plants sprout from their roots after they burn;
• the resin, coating the cones of closed-cone pines, melts in a hot fire and allows cones to open and disperse their seeds;
• perennial plants survive as underground bulbs and sprout quickly in response to the addition of nutrients to the soil after a fire;
• the rosette shape of yuccas, a plant that has been naturalized in various parts of Greece, protects the inner growth bud from destruction, in all but the hottest fires.

For more information about Mediterranean climate and flora, visit the Mediterranean Garden Society. Their site contains a plethora of interesting essays about Mediterranean Climate Gardening around the world.

Some of the information on this page has been obtained from the following great sites:

• Environment Canada;
• Mediterranean Garden Society;
• Weatherbase.