Recent National Weather Service guidance and ensemble forecasts indicate a minimum temperature near 56–58°F for San Francisco on September 3, driven by persistent marine-layer stratus and light onshore flow that limits nocturnal radiational cooling. Cloud cover and possible drizzle suppress temperature drops below the seasonal average low of ~56°F while preventing stronger cooling that would occur under clear skies. Model spread in boundary-layer moisture and wind speed creates the observed tight clustering of market-implied probabilities across the 52–65°F range, with the elevated 34.5% on 49°F or below reflecting residual tail risk from any unexpected clearing or stronger northerly drainage. Official minimum readings from downtown or SFO stations will resolve the market once diurnal cooling peaks overnight.