Forecast models from the National Weather Service show San Francisco’s July 19 high likely settling in the mid-to-upper 60s as a persistent marine layer moderates onshore flow and limits daytime heating. The closely matched market probabilities around 64–69 °F reflect small differences among ensemble runs in marine-layer depth, low-cloud clearance timing, and local sea-breeze strength. Cooler sea-surface temperatures along the central coast reinforce the onshore gradient, while any weakening of the subtropical high could allow slightly warmer air to reach the city. Traders are therefore weighting the most probable range near the climatological July average, with only modest upside risk if the layer erodes earlier than expected.