**Persistent marine layer influence and onshore flow are keeping San Francisco’s official high temperature expectations tightly clustered in the mid-to-upper 60s for June 25.** National Weather Service guidance and short-range models show a shallow marine layer with west-southwest winds of 10–20 mph limiting daytime warming near the coast, producing a forecast high near 63°F after morning clouds. Traders assign the highest implied probabilities to the 66–69°F range because small variations in layer depth, wind timing, or afternoon clearing can add a few degrees without breaking the overall cool pattern. Historical June climatology reinforces this narrow band, with rare excursions above 70°F under strong onshore regimes, while any model shift toward deeper mixing or reduced cloud cover could quickly favor the upper bins.