**Marine layer stability and consistent onshore flow are anchoring trader expectations for San Francisco’s overnight low on August 25 near the upper 50s.** Official National Weather Service forecasts and ensemble guidance from the past 48 hours project lows in the upper 50s, with several point forecasts centering on 58 °F under mostly cloudy skies and west-to-southwest winds of 5–15 mph. This aligns with the historical August average low of 56 °F while reflecting the moderating influence of the persistent marine layer that has kept recent daily minima in the mid-to-upper 50s. Model consensus shows limited spread, with only modest potential for a dip toward 56–57 °F if the marine layer deepens overnight or winds remain light; conversely, any clearing or slight offshore component could hold the minimum at 58–59 °F. No significant synoptic changes or heat intrusions are expected in the next 24 hours, keeping the market-implied probabilities concentrated on the 56–59 °F range as the most likely resolution outcomes.