Trader consensus around 58-59°F as the likely minimum reflects San Francisco’s persistent marine layer and onshore flow, which typically caps overnight lows near the long-term August average of 56-57°F at downtown and airport stations. Official National Weather Service observations at SFO recorded a 57°F minimum on August 23 under mostly cloudy skies with dew points near 55°F and light southwest winds, aligning with climatological norms and recent model guidance showing no strong offshore warming or clear-sky radiational cooling. The very low probabilities assigned to extremes below 54°F or above 60°F stem from the low historical variance in August coastal temperatures and the absence of any anomalous synoptic pattern, such as a heat ridge or strong northerly flow, that would shift the outcome outside the narrow 56-59°F band observed in the past week.