Recent forecasts from the National Weather Service and other models indicate San Francisco’s September 4 high will likely fall in the mid-to-upper 60s, cooler than the 70°F climatological average, due to a persistent marine layer deepened by an early-season cold front and unusually strong onshore flow. Trader sentiment reflects genuine uncertainty across the 62–80°F range because small differences in marine-layer depth, afternoon cloud clearance timing, and wind direction can shift maximum temperatures by several degrees; stronger marine influence or lingering low clouds suppress highs toward the lower bins, while any earlier thinning allows greater solar heating and pushes readings higher. Historical analogs show September extremes vary widely under similar patterns, and the next model runs plus real-time observations will further refine the most probable outcome.