Recent National Weather Service guidance and model consensus indicate a trough moving through western Washington will bring widespread cloud cover, showers, and cooler onshore flow to Seattle on September 13, suppressing daytime heating below the 71°F climatological average. Most official and ensemble forecasts converge on a high in the low-to-mid 60s, with the exact value hinging on the timing and intensity of rainfall, which can reduce insolation by 30–50% and limit boundary-layer warming. This uncertainty between 62–67°F explains the tight clustering of market-implied probabilities, as traders weigh the latest model runs showing potential for 63–67°F depending on convective development and wind shifts. Final NWS updates and morning observations on the 13th will refine resolution criteria tied to official Sea-Tac Airport readings.