Seattle, WA

Seattle's earthquake score of 74 sits at the 84th national percentile—the city's primary long-run hazard—and the 2001 Nisqually earthquake, which caused $305 million in damage across the Puget Sound region, remains the operational reminder that Seattle's seismic exposure is not an abstract geological fact. The 2021 Pacific Northwest heat dome reached 108°F in Seattle—a city where air conditioning penetration was below 50 percent and housing was built for a climate that assumed summer highs in the 70s. That event demonstrated a structural vulnerability: the temperate-weather brand that positions Seattle as a climate refuge is accurate for most of the year and catastrophically inaccurate during the specific atmospheric patterns that produce extreme heat. We checked twice: earthquake coverage is a separate economic decision for Seattle buyers—high deductibles, meaningful additional premium, and the risk of a Cascadia Subduction Zone event create a calculus that most buyers complete quickly and then defer indefinitely. Older housing in Northeast Seattle's 98115 without cooling systems faces the worst combination: seismic age-of-construction risk and heat-event vulnerability in the same building. South Lake Union's dense development changes heat and drainage assumptions relative to the established neighborhoods it has displaced. Annual premiums range from $1,200 to $3,000—stable, with risk expressed more through retrofit decisions than premium spikes. Heat at the 56th national percentile is low by ranking but strategically important given low AC penetration. Flood at the 43rd national percentile is low. The Seattle diligence checklist is seismic retrofit status, air conditioning availability, and building age—in that order. The temperate-weather reputation is not wrong. It is incomplete.

— Open Data Collective