Sonoma County, CA Outdoor Lighting: Dark Sky Rules (2026)

Section 26-90-120 of the Sonoma County Code sets the strictest night-sky standard in the county's zoning chapter, but it reaches only properties inside the LG/MTN (Local Guidelines/Taylor Sonoma Mayacamas Mountains) combining zone, as shown in the County's Zoning Database. Inside that boundary, the lighting rule sits in subsection (c)(2)d. under the Architectural Standards.

Seven separate limits apply. Exterior lighting must face downward, be fully shielded and sit at the lowest possible point to the ground to prevent glare and light pollution. Fixtures cannot be placed at the periphery of the property, and light cannot spill onto adjacent properties or into the night sky. Each luminaire is capped at one thousand (1,000) lumens per fixture. All exterior lighting operating at the same time cannot create more than one (1.0) lux beyond the property line. Roadway, parking and driveway lights must be low profile, full cut-off fixtures. Flood lights are not allowed at all. Any security lighting must be motion-sensor activated only.

The standards apply to single-family dwellings, residential accessory structures and associated site development such as roadways, grading and utilities, when those features are or would be visible from public roads. Exempt are accessory structures that need no Building Permit, agricultural structures and uses, farm family, agricultural employee and farmworker housing, and structures that are not or would not be visible from public roads at the time of construction. The section also states that it does not govern how a dwelling looks from a non-vehicular pedestrian, bicycle or equestrian trail open to the public.

The Department and the Board appointed local citizen advisory committees use these standards under Chapter 26, Article 64 (Scenic Resources Combining Zone) when they evaluate Building Permit applications for single-family dwellings and associated site development. A deed restriction must be recorded stating the conditions of the Design Review or Administrative Design Review approval, so the lighting limits follow the parcel to later owners. Legal dwellings and appurtenant structures that existed on the section's effective date are deemed to comply, but expansions must comply. The review authority can waive or modify one or more requirements only where strict compliance would render a legal parcel unbuildable. The current text reflects Ord. No. 6544 (12-9-2025) and Ord. No. 6532 (10-7-2025).