**Persistent marine layer influence and typical late-summer onshore flow are anchoring trader expectations for San Francisco’s August 31 minimum near 56–59 °F.** Official forecasts from the National Weather Service and private models show a mostly cloudy Monday with a low in the upper 50s (around 56–57 °F), consistent with the climatological average of 56.1 °F and recent nightly readings in the mid- to upper 50s. Cool Pacific waters (55–58 °F) and the California Current sustain a shallow marine layer that limits nocturnal radiative cooling while strong westerly winds maintain mixing. The closely matched leading bins (58–59 °F at 40.5 % and 56–57 °F at 32 %) reflect minor model spread in layer depth, inversion strength, and exact wind speeds overnight. Slightly stronger flow or a marginally deeper layer could push the minimum into the upper 50s, while any temporary thinning might allow brief additional cooling toward the mid-50s. Higher-probability bins above 66 °F capture residual uncertainty if the marine layer weakens more than expected, though current conditions and historical August patterns make this less likely. Lower bins below 52 °F remain discounted given the absence of unusual cold-air advection. Updated model runs and NWS briefings over the next 48 hours will be the key catalysts for any shift in consensus.