Marine layer advection from the Pacific, combined with persistent cloud cover and light onshore southwest winds, is suppressing radiational cooling and holding San Francisco temperatures near or slightly below seasonal norms for early September. Official forecasts from sources such as the National Weather Service and local models project an overnight low in the upper 50s, with current METAR observations at KSFO showing early-morning readings near 62°F before any further nocturnal drop. The tightly clustered market probabilities across the 50–63°F bins reflect uncertainty in exact wind mixing, marine stratus persistence, and any brief clearing that could allow an extra degree or two of cooling versus the more likely scenario of steady marine influence keeping the minimum in the mid-to-upper 50s. Historical climatology places the September 1 average low near 56°F, providing context for why sub-50°F outcomes remain heavily discounted.