**Marine layer stratus and onshore flow dominate the near-term outlook for San Francisco’s overnight minimum on August 22, keeping trader-implied odds tightly clustered between 54–61 °F.** Persistent high pressure over the Four Corners and a trough offshore have maintained the classic summer pattern of northwest winds advecting cool, moist air from the upwelled California Current. This favors fog and low stratus that typically bottom out in the mid- to upper-50s, aligning with the long-term August climatology of 57 °F and recent observed lows near 56 °F. Model guidance shows little spread in the 54–59 °F range, with resolution hinging on the precise timing of any marine-layer thinning before sunrise. The market’s near-even split among the four leading bins reflects genuine uncertainty around micro-scale variations in fog depth and wind speed rather than any large-scale deviation from seasonal norms.