Marine layer depth and onshore flow from the Pacific remain the dominant controls on San Francisco’s August 26 high temperature, with National Weather Service guidance indicating a shallow to moderate marine layer that should cap afternoon readings near 70–75 °F under mostly sunny skies. Recent model runs show modest disagreement on the timing of any late-day clearing or slight offshore wind shift that could allow a brief push into the upper 70s, while stronger westerly winds or lingering haze would favor the lower-70s bins. Historical climatology for late August supports this narrow range, with typical highs around 69–72 °F and rare excursions above 80 °F absent strong ridging. Traders appear to weigh the latest NWS and ensemble guidance most heavily, producing closely matched probabilities across the 74–77 °F outcomes as resolution nears.