Recent National Weather Service and model guidance points to a San Francisco low near 55–57 °F on September 27, driven by moderate onshore flow and a thinning marine layer that limits overnight radiative cooling. Trader consensus remains split between sub-47 °F and 66 °F-plus outcomes because small differences in stratus persistence, wind speed, or high-pressure ridging could shift the minimum several degrees either way. Historical September 27 lows average 55.5 °F with a record of 48 °F, underscoring that current conditions sit near the seasonal norm yet retain enough forecast spread to keep both tails competitive until final model runs and observations arrive.