National Weather Service forecasts for Seattle on August 15 project a high near 78°F under mostly sunny conditions with light winds, anchoring trader consensus around the 78-79°F range as the most probable outcome. Marine air influence and the absence of strong onshore flow or thermal troughs keep temperatures aligned with late-summer climatology, where daily highs typically peak in the mid-to-upper 70s. Ensemble guidance shows limited spread, with only modest potential for 80-81°F if afternoon heating exceeds model expectations, while cooler 76-77°F scenarios remain secondary given stable high pressure. No significant model shifts have emerged in the past 48 hours to alter this distribution.