An early September Pacific storm system is driving cooler-than-average conditions across western Washington, with official National Weather Service forecasts calling for widespread rain, showers, and possible thunderstorms on September 3. This setup favors onshore flow, persistent cloud cover, and limited daytime heating, producing a market-implied high most likely in the mid-60s°F. Ensemble guidance and NWS point forecasts converge on 64–67°F as the most probable range, reflecting uncertainty in exact timing of heaviest precipitation and any brief afternoon clearing that could allow modest warming. Historical September 3 highs average near 74°F, but the storm’s suppression of solar radiation and advection of cooler marine air explain the downward shift. Traders are weighting the 64–67°F bins most heavily because model spread remains modest two days out, while lower probabilities on 68°F+ or sub-62°F outcomes reflect the low likelihood of significant forecast busts before resolution.