Well-suited for farming, the bioregion is hot and dry in summer with long, sunny days. Winters are cool and often blanketed with heavy fog. The broad, flat valley is ringed by the Diablo and Coast Ranges on the west and the Sierra Nevada on the east.
Irrigation of this land with limited rainfall comes from two huge reservoir and canal systems that bring water from the length of the Sierras to the Valley farmers. The major river is the San Joaquin, with tributaries of the lower Stanislaus, Tuolumne, Merced, and Fresno rivers. The California Aqueduct extends the entire length of the region. The southern portion of the region includes the Kings, Kaweah, and Kern rivers, which drain into closed interior basins.