Recent National Weather Service and ensemble model guidance points to an overnight low in the upper 50s for San Francisco on August 23, 2026, aligning with the market’s tight clustering around the 56–59 °F bins. Persistent marine-layer stratus and moderate onshore flow under a typical summer thermal trough are expected to limit radiative cooling, keeping minimum temperatures near the long-term August average of roughly 56 °F at downtown and airport stations. Small variations in cloud cover timing or wind speed could shift the outcome within the 54–60 °F range, while the modest probability assigned to 49 °F or below reflects the low historical likelihood of anomalous clearing or offshore flow this late in the season. Updated model runs and official NWS briefings tomorrow morning will provide the final inputs before resolution.