Marine layer persistence and onshore flow from the cool Pacific are the dominant factors anchoring trader consensus around 68–73°F for San Francisco’s August 8 high, with the 70–71°F bin leading at 34% implied probability. National Weather Service guidance and recent model runs project a high near 70–72°F at KSFO under typical August conditions, where the marine inversion and sea breeze routinely suppress maxima below inland heat-wave levels. Key variables include fog clearance timing, inversion strength, and any subtle ridge amplification that could allow brief warming to 74°F or higher; conversely, stronger onshore winds or delayed clearing favor the 68–69°F outcome. This distribution reflects genuine forecast spread in a coastal regime where small shifts in boundary-layer conditions drive measurable temperature differences.