Official National Weather Service observations at San Francisco International Airport recorded a minimum temperature of 59°F on September 6, 2026, placing the daily low squarely in the 60-61°F market bin that now commands near-certain trader consensus. This outcome aligns with the typical early-September marine-layer regime, where onshore flow and coastal stratus moderate overnight cooling near the 56°F climatological normal. Model guidance and real-time METAR data showed limited diurnal spread under hazy conditions and moderate westerly winds, reducing the chance of colder readings at downtown or bay-side stations. A shift in resolution criteria to an alternate observing site or revised quality-control adjustment remains the primary realistic uncertainty, though historical practice favors the airport record for such contracts.