Traders have concentrated nearly half the market probability on a Seattle low of 58-59°F for August 22, reflecting the strong influence of typical late-summer marine air from the Pacific and Puget Sound that moderates overnight cooling. Persistent onshore flow, moderate humidity, and light winds under a weak high-pressure ridge kept radiative cooling limited, preventing temperatures from dropping into the mid-50s or lower. Official NOAA and NWS observations from Sea-Tac and downtown stations aligned with model consensus runs from the prior 48 hours, which showed minimal day-to-day variability and no incoming cold front or clear-sky enhancement that would push readings toward the lower-probability bins. With resolution criteria tied to verified daily minimums, the tight clustering around 58-59°F captures both historical climatology for the date and the absence of any recent atmospheric shift capable of altering the outcome.