S. sonomensis is found in three distinct areas in California: the California Coastal Range from Siskiyou to Napa county; from Monterey county to San Diego county; and in the Sierra Nevada foothills.
S. sonomensis is discovered in three separate regions in California: the Pacific Coastal Mountains from Siskiyou to Napa county; along the Central Coast from Monterey county to San Diego county; and in the Sierra Nevada mountain foothills.