Latest National Weather Service guidance for Seattle on August 25 highlights a marine layer and possible onshore flow that could cap daytime heating in the mid- to upper 70s, though partial afternoon clearing under a building upper ridge introduces upside potential into the low 80s. Key differentiators among the closely matched 80–89°F bins include the precise timing of cloud dissipation, wind direction shifts that modulate the marine push, and subsidence strength—stronger downslope flow would favor the higher bins while persistent low clouds or showers would anchor readings lower. Historical late-August norms near 74°F and recent model consensus around 76–79°F underscore the uncertainty traders are pricing across those central outcomes.