Marine layer and persistent onshore flow from the Pacific are the dominant factors capping San Francisco highs near or slightly above seasonal normals around 70°F on July 29. Official NWS guidance and model consensus point to a gradual warming trend midweek behind an expanding ridge, yet strong afternoon sea breezes and possible morning stratus should limit inland heat intrusion into the city. Recent Bay Area heat episodes have largely spared the immediate coast, keeping the distribution centered on 68–73°F bins. Key variables include marine-layer depth, wind speed and direction, and any late-day clearing that could allow an extra degree or two; traders price the highest uncertainty around these thresholds given typical July variability and the one-day forecast horizon.