Recent National Weather Service and ensemble model guidance points to an overnight low in the mid to upper 50s Fahrenheit for Seattle on September 10, driven by increasing cloud cover, light variable winds, and moderating marine air from the Pacific that limits radiational cooling. Forecast lows cluster around 56–59°F, consistent with the closely matched market-implied probabilities for the 56–57°F and 58–59°F bins. Historical September averages near 54°F provide context, but current conditions lack the clear skies or cold-air advection that would push readings lower. Minor differences among model runs on cloud timing and dew-point trends create the narrow spread between leading outcomes, with traders weighting the latest guidance and local station observations as the primary resolution inputs.