Recent National Weather Service and ensemble model guidance indicates a minimum temperature of 55–58°F in San Francisco on September 29, driven by clear skies, light westerly flow, and limited marine-layer influence that allows modest radiative cooling overnight. This aligns closely with the market’s leading 54–55°F outcome while keeping lower bins such as 47°F or below in contention only if stronger onshore advection or unexpected fog develops. Historical September 29 lows average 55.5°F with a record minimum of 49°F, providing climatological context for the current forecast spread. The next local NWS update and hourly observations through the overnight period will be the key data releases likely to shift trader positioning before resolution.