A cooling trend driven by a deepening marine layer and stronger onshore flow from the Pacific is suppressing daytime heating across coastal San Francisco, with National Weather Service guidance pointing to highs in the lower to mid-60s on August 13 amid lingering morning clouds and patchy drizzle potential. This follows a brief heat spike earlier in the week, as an upper-level trough enhances the typical summer marine influence that keeps San Francisco temperatures well below inland values. Model consensus on marine layer depth and afternoon clearing timing remains the key variable, producing closely matched market-implied odds around 66–69°F while lower-probability warmer outcomes would require unexpected layer erosion or reduced onshore winds.