**Forecast consensus from the National Weather Service and other models points to an overnight low in the upper 50s for San Francisco on August 23, 2026, with the 58–59 °F bin attracting the strongest trader positioning at 72.5 % implied probability.** Persistent onshore southwesterly flow and a well-established marine layer are the dominant influences, limiting radiative cooling while keeping skies mostly cloudy and suppressing daytime heating. Official NWS guidance and recent observations (including a 57 °F minimum on August 22) align closely with this range, consistent with the long-term August average low near 56 °F at downtown stations. Secondary bins such as 52–53 °F (25.5 %) and 54–55 °F (25.0 %) reflect residual uncertainty around exact minimum timing or localized microclimate effects near the coast, but current model runs show limited downside risk. No significant synoptic shifts—such as offshore flow or clearer skies—are expected before sunrise, supporting the market’s tight clustering around upper-50s values.