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

Sonoma County does not impose one comprehensive dark-sky lighting ordinance on every parcel; instead, shielding and glare requirements are built into the development standards for specific uses within the County Zoning Regulations (Chapter 26) and applied through design review (Article 82). A recurring standard appears across several special-use sections in Article 88: exterior lighting must be fully shielded and downward-casting so it does not wash out onto structures, neighboring properties, or the night sky. For instance, the County's recent housing-element ordinance (No. 6458) and related special-use standards require exterior lighting to be fully shielded and downward-facing, prohibit floodlights and uplights, and impose lumen and spillover limits for certain uses (for example, requiring fixtures not to exceed 1,000 lumens and total illuminance beyond the property line not to exceed 1.0 lux in specified contexts such as homeless shelters). Solar facility standards (Sec. 26-88-206) require that concentrated reflections or glare not be directed at occupied structures, recreation areas, roads, highways, or airports. New development subject to design review (Sec. 26-82-050) is evaluated for lighting that avoids glare and spillover onto adjacent properties. Property owners in scenic corridor and rural areas should expect shielded, downcast fixtures to be required, while ordinary single-family yard lighting is governed mainly through nuisance and design-review provisions rather than a fixed lumen cap.