**Forecasts from the National Weather Service and multiple models point to a lowest temperature in San Francisco on August 31 in the upper 50s, driven by a deepening marine layer and moderate onshore flow.** Recent NWS discussions note stratus reforming overnight into Monday with a layer around 2,000 feet deep, limiting radiative cooling while stronger southwest winds (10–20 mph) promote mixing. This follows a milder weekend and aligns with typical late-August conditions, where the Pacific-driven marine layer caps daytime highs and prevents sharp overnight drops. Historical averages place the August 31 low near 56°F, with records rarely dipping to 51°F; current guidance centers on 57°F, supporting the tight clustering of market probabilities around 54–59°F. Minor differences among leading bins reflect small uncertainties in exact marine layer depth, wind gusts, and cloud timing, which can shift the minimum by a degree or two. Stronger-than-expected winds or earlier clearing could nudge readings higher, while deeper stratus and lighter flow favor the lower end of the range. No unusual heat or offshore flow is indicated that would push outcomes outside the mid-50s.