Recent National Weather Service and ensemble model guidance points to a high around 78–81°F for Seattle on August 21, driven by persistent high pressure over the Pacific Northwest combined with a moderating marine layer from Puget Sound that limits afternoon heating. This setup aligns with the market’s heaviest trading on the 80–81°F and 78–79°F bins, as climatological August highs average near 76°F but the region’s 14th consecutive warmer-than-normal summer has elevated baseline temperatures. Short-range model runs show minimal day-to-day variability through the period, with only modest onshore flow expected to cap readings below 85°F and keep probabilities of 86°F or higher under 4%. Updated NWS briefings tomorrow morning will provide the final observational inputs used for market resolution.