Recent National Weather Service guidance and ensemble models indicate Seattle highs in the mid-70s on August 12, driven by a persistent marine layer and onshore flow off Puget Sound that limits afternoon warming. This aligns with trader consensus favoring the 74–77°F brackets amid typical late-summer climatology, where average daily maxima near 77°F are moderated by sea breezes and variable cloud cover. Subtle differences in solar insolation, boundary-layer mixing, and any late-day clearing create the tight spread between leading outcomes, while above-normal seasonal temperatures provide a slight upward bias without pushing into the low 80s. Final official observations will resolve the market.