Recent National Weather Service forecasts and ensemble models indicate San Francisco highs on September 4 will likely fall in the upper 60s to low 70s Fahrenheit, driven by a persistent marine layer of cool, moist Pacific air that limits daytime warming despite seasonal averages near 70°F. Southwesterly flow and residual moisture from midweek systems are expected to keep the layer intact, suppressing temperatures below potential heat-wave thresholds while allowing partial clearing. This scientific consensus on marine influence and below-normal 850 mb temperatures underpins trader positioning, with the strongest implied probabilities clustered on 68–71°F bins. Forecast uncertainty remains from variable layer depth and wind shifts, with updated model runs and observations likely to refine odds before resolution.