This region lies on both sides of equator between 30° to 45° latitudes on the western coasts of the continents within Temperate region.
Mediterranean climate, major climate type of the Köppen classification characterized by hot, dry summers and cool, wet winters and located between about 30° and 45° latitude north and south of the Equator and on the western sides of the continents. In the Köppen-Geiger-Pohl system, it is divided into the Csa and Csb subtypes.
Poleward extension and expansion of the subtropical anticyclone over the oceans bring subsiding air to the region in summer, with clear skies and high temperatures. When the anticyclone moves Equator-ward in winter, it is replaced by traveling, frontal cyclones with their attendant precipitation. Annual temperature ranges are generally smaller than those found in marine west coast climates, since locations on the western sides of continents are not well positioned to receive the coldest polar air, which develops over land rather than over the ocean. Mediterranean climates also tend to be drier than humid subtropical ones, with precipitation totals ranging from 35 to 90 cm (14 to 35 inches); the lowest amounts occur in interior regions adjacent to the semiarid steppe climates.
Some coastal locations (such as southern California in the western United States) exhibit relatively cool summer conditions and frequent fogs where cold offshore currents prevail. Only in Europe, where the latitude for this climate type fortuitously corresponds to an ocean basin (that of the Mediterranean Sea, from which this climate derives its name), does this climate type extend eastward away from the coast for any significant distance.
In the formulas above, r is average annual precipitation total (mm), and t is average annual temperature (°C). All other temperatures are monthly means (°C), and all other precipitation amounts are mean monthly totals (mm).
2Any climate that satisfies the criteria for designation as a B type is classified as such, irrespective of its other characteristics.
3The summer half of the year is defined as the months April–September for the Northern Hemisphere and October–March for the Southern Hemisphere.
4Most modern climate schemes consider the role of altitude. The highland zone has been taken from G.T. Trewartha, An Introduction to Climate, 4th ed. (1968).
Data Sources: Adapted from Howard J. Critchfield, General Climatology, 4th ed. (1983), and M.C. Peel, B.L. Finlayson, and T.A. McMahon, "Updated World Map of the Köppen-Geiger Climate Classification," Hydrology and Earth System Sciences, 11:1633–44 (2007).