Issaquah, WA Outdoor Lighting: Dark Sky Rules (2026)

Issaquah's outdoor lighting chapter, Chapter 18.610 of the Land Use Code, is built on the 2011 Model Lighting Ordinance from the International Dark Sky Association and the Illuminating Engineering Society of North America, and its stated purposes include curtailing light pollution and reducing skyglow. The operative dark sky rule sits in Table 18.610.060(E)(1), Technical Lighting Requirements, which applies to every performance method used for nonresidential and multifamily projects.

The table sets two linked rows. Dark sky hours run between 10:00 p.m. and 6:00 a.m., or from 30 minutes after the close of a business or entity with outdoor lighting to 30 minutes before its opening, whichever provides more dark sky. During those hours, total outdoor lighting must be reduced by at least 30 percent or extinguished. The reduction includes low voltage landscape lighting, and it must be applied uniformly across the site: an owner cannot pick individual luminaires to switch off while leaving others at full output.

The code lists six exceptions in which no dark sky reduction is required. They cover code required lighting for steps, stairs, walkways, and building entrances, City facilities that set lighting hours based on the facility's hours, motion activated lighting or lighting on an astronomic clock with a manual override that meets § 18.610.080(B)(4), businesses or entities that operate on a 24-hour basis, residential properties that qualify under § 18.610.070, and properties whose outdoor lighting consists of only one luminaire. Section 18.610.080(B)(4) adds that motion sensors or astronomic clocks can be activated for no more than five minutes unless a longer period is objectively demonstrated, and that motion sensors cannot be triggered by off-site movement. Elsewhere, Table 18.610.030(B) places each zoning district in a lighting zone from LZ 0 to LZ 4, and the lower zones carry the strongest expectation that lighting is extinguished or reduced after dark sky hours.