**Official observations from Seattle-Tacoma International Airport and National Weather Service reports recorded a daily maximum of 64°F on September 30, 2026, under overcast skies with light northerly winds and no measurable precipitation.** This aligned closely with the seasonal average high of approximately 65.6°F for the date and reflected typical early-autumn marine influence moderating temperatures in the region. Recent model guidance and surface analyses showed stable atmospheric conditions without the clear skies or downslope warming that could push readings higher, producing the narrow 64–65°F band captured by trader consensus at 100% implied probability. The market’s strong positioning rests on verified station data rather than forecasts, as the date had already passed. While official climate summaries are rarely revised substantially, an unexpected post-processing correction or a localized microclimate difference at the primary reporting site could theoretically alter the final figure, though historical precedent shows such changes are minimal for daily maximum temperatures.