The closely matched market-implied odds for 52–53°F and 54–55°F lows in Seattle on September 14 stem from uncertainty in the precise minimum recorded at official stations such as Sea-Tac Airport. Key differentiating factors include the strength and timing of the marine layer, which moderates nocturnal cooling over Puget Sound, versus clear-sky radiative cooling that can drop temperatures 2–4°F below model guidance. Recent atmospheric conditions, including any weak frontal passage or wind shifts, further influence whether the low registers in the lower or higher bin. Official NOAA and National Weather Service verified observations will resolve the market once quality-controlled data are released.