The San Bernardino Valley, centered approximately at 34°04' N, 117°17 'W, lies at the south base of the Transverse Ranges. It is bordered on the north by the western San Gabriel Mountains and San Bernardino Mountains, on the east by the San Jacinto Mountains, and on the south and west by the Santa Ana Mountains and Pomona Valley. Elevation varies from 180 to 210 m on valley floors near Chino, where it gradually increases to about 360 to 420 m near San Bernardino and Redlands. The valley floor houses roughly over 80% of the over 4 million total human population in the Inland Empire region, one of the most important industrial and residential areas of Southern California.
The climate is Mediterranean with cool, wet winters and dry, warm summers. Sage scrub is the predominant natural vegetation along washes and uplands; it intergrades with chaparral at elevations of 600 to 700 m. Other vegetation consists of a patchwork of grasslands, riparian woodlands, and mixed hardwood forests, which border the valley in the mountains on the north and east.
The San Bernardino valley was cut from fast moving water flows from mountain ranges in the north, east and south that collectively drain into the Santa Ana River basin that goes to the sea through Riverside and Orange County. The valley connects several open natural areas and beautiful mountain and valley vistas. The San Bernardino Valley is surrounded by preserves, national forests and open recreational areas. For this reason many residents travel through the area for a variety of outdoor sports, including skiing, hiking, biking and ballooning in the mountain resorts of Crestline, Lake Arrowhead and Big Bear City.
The Santa Ana winds blow into the valley from the Cajon Pass, which exits the valley's north end between the San Gabriel and San Bernardino mountains. Once part of famed U.S. Route 66, it is now crossed by Interstate 15 on its way through the high desert. Interstate 10 enters the valley from Pomona and exits to the east over the San Gorgonio Pass, which enters into the low desert.
Joan Didion, in her essay "Some Dreamers of the Golden Dream," describes the San Bernardino Valley as "...in certain ways an alien place: not the coastal California of the subtropical twilights and the soft westerlies of the Pacific but a harsher California, haunted by the Mojave just beyond the mountains, devastated by the hot dry Santa Ana wind that comes down through the passes at 100 miles an hour and works on the nerves.
The valley's cities include:
Major highways include:
National forests surrounding the valley include: