Persistent marine layer influence and moderate onshore flow from the Pacific are positioning San Francisco’s overnight low for August 29 near the mid-50s, with National Weather Service guidance and ensemble models showing lows of 55–57°F under variable stratus and light westerly winds. Coastal upwelling of cold water combined with the typical late-summer marine layer depth limits radiational cooling, keeping temperatures clustered in the 54–59°F range that accounts for the top three market-implied outcomes (56–57°F at 45.5%, 58–59°F at 29.0%, 54–55°F at 25.0%). Recent model runs indicate only modest spread in boundary-layer moisture and wind speed, supporting tight trader consensus around these bins while lower-probability tails reflect the small chance of clearer skies or stronger winds allowing slightly more cooling.