<P> The Transverse Ranges include a series of east--west trending mountain ranges that extend from Point Conception at the western tip of Santa Barbara County, eastward (and a bit south) to the east end of the San Jacinto Mountains in western Riverside County . The Santa Ynez Mountains make up the westernmost ranges, extending from Point Conception to the Ventura River just west - northwest of Ojai, in Ventura County . Pine Mountain Ridge, Nordhoff Ridge--Topatopa Mountains, Rincon Peak--Red Mountain, Sulphur Mountain, Santa Paula Ridge, South Mountain--Oat Mountain--Santa Susana Mountains, Simi Hills, Conejo Mountains--Santa Monica Mountains are all part of the Western Transverse Ranges, in Ventura and western Los Angeles counties . </P> <P> The Liebre Mountains occupy the northwest corner of Los Angeles County, and represent a northwestern extension of the San Gabriel Mountains, both on the Pacific Plate side of the San Andreas Fault . The fault divides the San Gabriel Mountains from the San Bernardino Mountains further to the east in San Bernardino County . </P> <P> It is possible to surf in the Pacific Ocean and ski on a mountain during the same winter day in Southern California . </P> <P> There are harsh deserts in the Southeast of California . These deserts are caused by a combination of the cold offshore current, which limits evaporation, and the rain shadow of the mountains . The prevailing winds blow from the ocean inland . When the air passes over the mountains, adiabatic cooling causes most water in the air to rain on the mountains . When the air returns to sea level on the other side of the mountains, it recompresses, warms and dries, parching the deserts . When the wind blows from inland, the resulting hot dry katabatic winds are called the Santa Ana Winds . </P>

The western boundary of what directly borders california