Trader consensus heavily favors a 54-55°F low for Seattle on September 17, driven by National Weather Service observations and model runs showing clear skies, light winds, and radiative cooling under moderate dew points near 50°F. This aligns with the seasonal climatology of 52.9°F average lows at Sea-Tac and recent nights recording 52-54°F minima amid stable high pressure. Official preliminary data indicate an actual low near 56°F, consistent with the market's strong implied probability. Shifts in cloud cover, increased wind, or a late frontal passage could push readings into the low 50s, though such developments were not supported by the latest model consensus or station reports.