Trader consensus for Seattle’s August 21 minimum temperature centers on the 56–61°F range, with 58–59°F holding the highest implied probability at 40.5%. National Weather Service forecasts and model guidance indicate clear skies, light northerly winds, and a shallow marine layer favoring overnight radiative cooling to around 58°F. This aligns with late-August climatology, where Seattle averages near 57°F for daily lows under similar high-pressure patterns. Recent observations show stable onshore flow without significant cloud cover or frontal systems that could moderate temperatures. Uncertainty in exact minimum readings stems from station siting differences and precise timing of the daily low, keeping adjacent bins competitive while lower or higher outcomes remain low-probability outliers.