Recent deepening of the marine layer along the California coast, combined with persistent onshore flow, has driven a cooling trend that positions San Francisco's highest temperature on August 13 most likely in the 66–69°F range per National Weather Service guidance. This setup limits solar heating and maintains afternoon highs several degrees below seasonal norms, consistent with observed coastal readings in the mid-60s amid patchy drizzle potential. NOAA model consensus and recent buoy data show no strong offshore warming signal through the period, though minor clearing could allow a brief push toward 68–70°F. Traders have weighted these factors heavily against historical August averages near 69°F, with resolution hinging on official maximum observations from central city stations.