Superior Region

The northern third of California, stretching from the coast to the Nevada and Oregon borders.

Counties

Butte • Colusa • Del Norte • Glenn • Humboldt • Lake • Lassen • Mendocino • Modoc • Nevada • Plumas • Shasta • Sierra • Siskiyou • Tehama • Trinity

Bay Area Region

The San Francisco Bay Area and surrounding coastal counties in the middle third of the state.

Counties

Alameda • City of Berkeley • Contra Costa • Marin • Monterey • Napa • San Benito • San Francisco • San Mateo • Santa Clara • Santa Cruz • Solano • Sonoma

Central Region

The Gold Country, Sierra, and Central Valley counties in the middle of the state to the Nevada border. 

Counties

Alpine • Amador • Calaveras • El Dorado • Fresno • Inyo • Kings • Madera • Mariposa • Merced • Mono • Placer • Sacramento • San Joaquin • Stanislaus • Sutter-Yuba • Tulare • Tuolumne • Yolo

Los Angeles Region

Los Angeles County (and only Los Angeles County).

Major Cities

mixed

Southern Region

The southern third of California, stretching from the coast to the Arizona and Mexico borders. 

Counties

Imperial • Kern • Orange • Riverside • San Bernardino • San Diego • San Luis Obispo 
• Santa Barbara • Tri-Cities Mental Health Services • Ventura