Recent National Weather Service guidance and ensemble model consensus center Seattle’s August 18 high in the upper 70s, producing the market’s tight split between 76-77°F (32.5%) and 78-79°F (28.0%). A warmer-than-average summer pattern has kept mid-August climatology near 77–79°F, with typical afternoon sea-breeze and marine-layer influences that cap daytime maxima. Minor forecast differences in cloud timing, subsidence strength under high pressure, and the exact onset of onshore flow create the observed uncertainty across adjacent bins, while lower-probability outcomes above 80°F or below 74°F reflect limited model support for stronger warming or cooling anomalies on this date.