San Francisco's marine layer and onshore flow from the Pacific are the dominant controls on July 11 highs, typically capping afternoon temperatures near the 68–70°F seasonal average by limiting solar heating and promoting stratus and fog. Current forecast guidance points to a modest marine push with possible partial clearing, placing the most likely outcomes in the 68–71°F range and explaining why those two bins hold the highest implied probabilities at 25.5% and 26.5%. Model consensus remains tight because July climatology rarely produces extremes in the city proper; small differences in wind direction, inversion strength, or timing of any clearing will decide whether the high settles at 68–69°F or edges into 70–71°F. Traders are weighting the historical base rate heavily while awaiting the final National Weather Service forecast updates before resolution.