Recent National Weather Service forecasts and ensemble guidance indicate a low around 50–52°F for Seattle on September 23 under continued onshore flow and broad upper-level troughing over the Pacific Northwest. This pattern sustains morning low clouds and marine air advection, suppressing overnight radiative cooling while limiting daytime highs to the mid-60s. Historical climatology places average September lows near 51–53°F, so current conditions align closely with seasonal norms rather than extremes. Model consensus shows minimal spread for the overnight minimum, with the primary uncertainty tied to exact timing of any weak disturbance and cloud cover persistence. Traders are weighting the 52–53°F bin highest because fresh model runs have stabilized near that threshold ahead of the final evening observations used for market resolution.