Persistent marine layer and cold Pacific waters via the California Current and coastal upwelling are anchoring San Francisco highs near seasonal norms around 67–70°F on August 28. National Weather Service guidance and recent model runs point to morning stratus with west winds of 10–20 mph limiting afternoon warming, after several warmer days earlier in the week. Differentiation among the tightly bunched 66–71°F market leaders hinges on exact sea-breeze strength, inversion-layer depth, and how quickly any coastal clouds erode—small shifts in these variables can swing the peak by a degree or two. Trader positioning around these bins reflects both climatological precedent and the inherent uncertainty in microscale coastal forecasts.