Recent National Weather Service and local model guidance indicate Seattle's August 21 high will likely peak in the low 80s, driven by moderate subsidence under a building Pacific high that limits onshore marine flow and allows greater daytime solar heating. Light northwest winds and partial afternoon clearing further support temperatures several degrees above the 77°F seasonal normal at Sea-Tac, though a lingering shallow marine layer or earlier sea breeze could cap readings near 80°F. Trader consensus clusters tightly around 80–83°F because small differences in boundary-layer moisture, cloud timing, and exact wind shift determine whether the daily maximum reaches the upper or lower end of that range, with higher bins remaining improbable absent strong offshore flow.