The Cascades then extend southeastward until they merge into the Sierra Nevada.  In the north the Cascades range generally from 5,000 to 10,000 feet in height, with spectacular Mt. Shasta rising to 14,161 feet.  Farther south the Sierra Nevada rise to over 10,000 feet in elevation.  The Sierra Nevada, like the Coast Range, parallel the coast, but the crest over most of its length is about 150 miles inland.  Thus, between the two ranges there is a broad, flat valley averaging 45 miles or more in width.  In the vicinity of latitude 35 degrees North the Sierra Nevada meets the Tehachapi Mountains, which bend southwestward to join the Coast Range, closing off the southern end of the Central Valley.

From the point where the Tehachapi and the Coast Range join, a series of ranges extend southeastward to the southern border of the State.  West of these ranges are basins that have a predominantly maritime climate, while to the east a continental desert regime prevails.

Both the extreme northeastern portion of California and the desert area of southern California east of the mountains lie within the Grerat Basin.  The Great Basin extends from Utah to the Sierra Nevada and has no surface drainage to the ocean.  It is an area of climatological extremes.  In northeastern California, for example, Boca is the coldest reporting point in the State.  Included in the deserts of the south are Death Valley and the Mojave Desert which are the hottest and driest parts of the State.