Trader consensus clusters around 76–79°F as the most probable peak for Seattle on August 18 because official forecasts from the National Weather Service and local models converge on a high near 77–78°F under a weak marine layer and light southerly flow. Persistent onshore winds and a shallow stratus deck limit daytime heating despite seasonal solar angles, keeping readings close to the mid-August climatological normal of 76–78°F at Sea-Tac Airport. Small differences among the top brackets hinge on the exact timing of any afternoon clearing and the strength of the Puget Sound convergence zone, which can add or subtract 1–2°F depending on boundary-layer mixing. Recent model runs show minimal spread, with no strong ridge or thermal trough expected to push values higher.