Twain Harte, CA Outdoor Lighting: Dark Sky Rules (2026)

Unincorporated Tuolumne County controls outdoor lighting through its Title 17 (Zoning) standards rather than a separate named dark-sky ordinance. The County's adopted Objective Site and Design Standards (effective April 2024 under Title 17, Chapter 17.100) set the County's documented exterior-lighting requirements. The stated intent is to provide sufficient lighting for safety while reducing light spill and over-illumination. Under the design-and-placement standard, lighting shall be recessed or hooded, downward-directed, and located to illuminate only the intended area; exposed bulbs are prohibited and colored bulbs and lenses are prohibited. For common areas in multi-unit and mixed-use projects, exterior lighting must be fully shielded and restrain light to a minimum of 30 degrees below the horizontal plane of the light source, fixtures are limited in height, lighting must be arranged so it will not shine directly onto adjacent residentially zoned land, and uplighting is prohibited. These objective standards apply most directly to multi-unit, mixed-use, and design-review projects, but the underlying goals - shielding, downward direction, and no spill onto neighbors - reflect the County's approach to exterior lighting generally. Because much of the County is rural and dark, these shielding and spill controls function as the practical dark-sky rules. Property owners undertaking new development, especially in design-review communities such as Columbia, Jamestown, Twain Harte, and Tuolumne, should design exterior lighting to be fully shielded and downward-directed. Confirm the applicable lighting standards for a specific project with the Community Development Department.