Forecast models from the National Weather Service and private sources indicate a typical late-summer marine layer over San Francisco on August 17, with onshore westerly winds and possible morning fog limiting afternoon warming to the upper 60s or low 70s. This setup aligns with climatological norms of 68–70°F highs for mid-August and explains the near-even market split between the 68–69°F and 70–71°F bins. Minor differences hinge on exact cloud clearance timing and wind strength, both of which can shift peak readings by a degree or two. No offshore flow or ridge strengthening is projected that would support higher readings, keeping probabilities concentrated in the narrow range around the seasonal average.