**Incoming upper-level trough and onshore flow are driving trader focus on Seattle's minimum temperature for August 22, with forecasts centering on 58–61 °F amid model spread.** National Weather Service and ensemble guidance show a transition from warm, mostly clear conditions on the 20th–21st to increasing cloud cover, light south-to-southwest winds, and a 30–60% chance of showers or drizzle as the trough approaches the Pacific Northwest. These factors limit radiational cooling overnight while marine air moderates daytime highs near 70 °F. Slight differences in timing of cloud onset, precipitation, and wind strength across models produce the tight clustering around 58–59 °F, 60–61 °F, and 64–65 °F outcomes. Historical August 22 lows average near 56 °F, but the current pattern favors a milder night than climatology. Updated NWS and model runs tonight will likely narrow the market-implied odds ahead of resolution.