Situated on the Pacific coast between latitudes 30 and 45 N. is a zone subject to alternate wet and dry seasons, the transition zone between the dry west coast desert and the wet west coast.
Trewartha (1968) classifies the climate of these lands as Cs, signifying a temperate rainy climate with the dry, hot summers indicated by the symbol s (see Appendix 2, climate diagram for Pasadena, California). The combination of wet winters with dry summers is unique among climate types and produces a distinctive natural vegetation of hardleaved evergreen trees and shrubs called sclerophyll forest. Various forms of sclerophyll woodland and scrub are also typical. Trees and shrubs must withstand the severe summer drought--2 to 4 rainless months--and severe evaporation.
Soils of this Mediterranean climate are not susceptible to simple classification. Alfisols and Mollisols typical of semiarid climates are generally found.