Current forecast models from sources like the National Weather Service and AccuWeather indicate San Francisco highs near 66–70°F on August 20, aligning with the market’s tight clustering around 68–71°F outcomes. Primary drivers include the persistent summer marine layer, cool sea-surface temperatures from coastal upwelling, and moderate westerly onshore flow that limits daytime heating and promotes fog or low stratus. Minor model differences in cloud timing, wind strength, and boundary-layer mixing explain the narrow spread between 68–69°F and 70–71°F bins; stronger winds or earlier fog clearance could push readings toward the higher end, while thicker marine influence favors the lower. Historical August averages near 67–70°F provide context, with no major heat advection or offshore wind events altering the pattern recently.