Trader consensus reflects substantial uncertainty around Seattle's peak temperature on August 20, with roughly equal implied probabilities across the 76–85°F range. Primary drivers include variable onshore marine flow from the Pacific, which moderates daytime heating, and the strength of any marine layer or morning stratus that could limit solar insolation. Recent NWS guidance and model runs point to partly cloudy conditions with highs near 78–80°F, consistent with climatological averages of about 76°F for the date and the influence of a weak ridge allowing mild warming without extreme heat. Key differentiating factors are exact cloud timing, wind direction shifts, and any subtle high-pressure adjustments that could add or subtract a few degrees. Updated forecast discussions from the National Weather Service or morning observations on August 20 will likely refine these probabilities ahead of market resolution.