Subregions- Arizona
 - Bakersfield urban area, California
 - Central California
 - Channel Islands region, California
 - Crater Lake area, Oregon
 - Craters of the Moon area, Idaho
 - Fresno urban area, California
 - Greater Los Angeles area, California
 - Gulf of Santa Catalina, California
 - Lassen Peak area, California
 - Las Vegas urban area, Nevada
 - Long Valley area, California
 - Medicine Lake area, California
 - Mexicali-Calexico urban area, California
 - Mexicali urban area, Baja California, Mexico
 - Monterey Bay, California
 - Mount Bachelor area, Oregon
 - Mount Hood area, Oregon
 - Mount Jefferson area, Oregon
 - Mount McLoughlin area, Oregon
 - Mount Shasta area, California
 - Mount Washington-Belknap Crater area, Oregon
 - Nevada
 - Newberry Caldera area, Oregon
 - Northern California
 - northern Idaho
 - offshore Central California
 - offshore Northern California
 - offshore Oregon
 - off the coast of California
 - off the coast of Northern California
 - off the coast of Oregon
 - Oregon
 - Phoenix urban area, Arizona
 - Sacramento urban area, California
 - San Clemente Island, Channel Islands, California
 - San Diego County urban area, California
 - San Francisco Bay area, California
 - San Francisco Bay, California
 - San Miguel Island, Channel Islands, California
 - San Nicolas Island, Channel Islands, California
 - San Pablo Bay, California
 - San Pedro Channel, California
 - Santa Barbara Channel, California
 - Santa Catalina Island, Channel Islands, California
 - Santa Cruz Island, Channel Islands, California
 - Santa Monica Bay, California
 - Santa Rosa Island, Channel Islands, California
 - Southern California
 - southern Idaho
 - Stockton urban area, California
 - Sunset Crater area, Arizona
 - Three Sisters area, Oregon
 - Tijuana urban area, Baja California, Mexico
 - Tucson urban area, Arizona

| |