Riverside County Ord. 655 protects Mt. Palomar Observatory through one of the strongest dark-sky lighting laws in the United States, restricting outdoor lighting type, intensity, and curfews across western Riverside County.
Ord. 655 establishes Zones A and B around Mt. Palomar Observatory, governing properties within 15 and 45 miles respectively. The ordinance limits outdoor lighting to fully shielded fixtures, prohibits new mercury vapor and most metal halide installations, and requires low-pressure sodium or filtered LED for many uses. Commercial and digital signs face strict lumen caps and 11 p.m. curfews in Zone A. Communities such as Temecula, Murrieta, Hemet, and unincorporated areas comply countywide alongside San Diego County's matching ordinance, jointly preserving research conditions for Caltech's observatory.
Code Compliance issues correction notices and administrative citations; unshielded billboards and noncompliant LED conversions must be replaced or retrofitted with proper optics.
See how Riverside County's billboard lighting rules stack up against other locations.
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