Latest National Weather Service guidance and ensemble models indicate a daytime high near 68°F for San Francisco on May 17, driven by a weakening marine layer and slightly warmer onshore flow that allows modest afternoon warming. This positions the 68°F-or-higher outcome at the market-leading 53.5% implied probability. Typical May climatology features persistent coastal stratus that caps highs near the 67°F seasonal average, yet recent model runs show reduced fog coverage compared to the past week’s cooler pattern. Traders weigh these factors against historical variability at the KSFO station, where small shifts in wind direction or cloud timing can move the final reading by 2–3°F. Updated forecast discussions are expected within the next 12 hours.