Current National Weather Service forecasts and ensemble model guidance indicate Seattle’s overnight low on September 5 will settle in the low-to-mid 50s°F, aligning with the market’s tight clustering around 52–55°F. Light northerly winds, increasing mid-level cloud cover, and a marine-influenced airmass with dew points near 50°F are limiting radiative cooling and preventing a deeper drop below 52°F, while the absence of strong cold advection keeps temperatures from rising above the mid-50s. Historical climatology shows early-September lows averaging 54–55°F at Sea-Tac, providing context for why traders assign meaningful probability to both the 52–53°F and 54–55°F bins. Updated model runs tonight will clarify whether any last-minute clearing can push readings toward the lower edge of that range.