Official observations from Seattle-Tacoma International Airport recorded a daily maximum of 67°F on September 23, 2026, at 4:21 PM local time, placing the outcome squarely in the 66-67°F range. This value fell just below the 1991-2020 climatological average high of 68.3°F under overcast skies, light southerly winds, and no measurable precipitation. National Weather Service climate summaries confirm the reading with high reliability, aligning with pre-event model guidance that had trended cooler than earlier forecasts near 69°F. The market's near-certain consensus reflects the finality of verified station data, though minor uncertainty could arise from rare post-analysis revisions or differences between official airport readings and other local sensors.