Pima County, AZ Outdoor Lighting: Dark Sky Rules (2026)

The Pima County Outdoor Lighting Code (Chapter 18.81 of the Pima County Zoning Code) was first adopted in 1974 and has been strengthened multiple times to protect the astronomical research at Kitt Peak National Observatory (located within Pima County on the Tohono Oodham Nation). Key provisions: all outdoor luminaires must be fully shielded (full-cutoff) so no light is emitted above the horizontal plane. Maximum correlated color temperature (CCT) is 3000K (warm white) -- no cool-white or daylight LEDs are permitted for outdoor use. The code establishes three lighting zones based on proximity to Kitt Peak, with the most restrictive zone (Zone A, within approximately 19 miles of the observatory) limiting total lumens per acre to very low levels. Zone B covers most of unincorporated Pima County with moderate lumen limits. Zone C covers areas closer to Tucson. All new construction, renovations, and fixture replacements must comply. Decorative, architectural, and commercial lighting must meet shielding and CCT requirements. Mercury vapor, metal halide, and unshielded fluorescent fixtures are prohibited in new installations. Gas station canopies, parking lots, and commercial signage are subject to specific lumen and shielding standards. The code is enforced by Pima County Development Services and has been a model for dark-sky ordinances nationwide.