Trader consensus has locked in 66-67°F as the official high for Seattle on September 12 because National Weather Service observations at Sea-Tac Airport recorded a maximum temperature in that narrow band amid widespread rain, persistent low clouds, and southerly flow. These conditions suppressed daytime warming well below the 1991-2020 September 12 climatological average of 71°F, consistent with model guidance showing a cool marine air mass and minimal solar insolation. Official preliminary climatological data (CF6) and hourly METAR reports align precisely with this outcome, leaving negligible room for alternative bins. Only an unlikely post-processing revision to the daily maximum or a station-specific discrepancy could alter the result before final certification.