Short-term National Weather Service guidance and ensemble models converge on a Seattle high near 77–78°F for August 18 under moderate onshore flow from the Pacific and Puget Sound, typical of mid-August climatology when average highs reach about 77°F. A weak ridge provides limited warming while marine air keeps extremes in check, favoring the closely matched 76–79°F bins that dominate trader positioning. Minor differences among outcomes hinge on afternoon cloud cover, exact wind direction, and boundary-layer mixing, any of which can shift the peak by 1–2°F. The broader warmer-than-average summer pattern supports the slight upside tilt but does not override the stable short-range consensus ahead of tomorrow’s resolution.