Trader consensus clustering on 70–73°F for Seattle’s October 4 high reflects National Weather Service and private model agreement on a strong high-pressure ridge delivering sunny afternoon conditions and above-average diurnal heating. Morning marine-layer stratus or patchy fog is expected to clear under light northerly flow, allowing temperatures to climb several degrees above the 64°F climatological normal. Minor spread among leading bins stems from small differences in simulated cloud timing, boundary-layer mixing, and peak insolation across ensemble members, with limited upside risk above 74°F given the season’s declining solar angle and persistent onshore influence. Updated model runs and NWS briefings through October 3 will refine exact maxima before market resolution.