**A shallow marine layer and persistent onshore westerly flow from the eastern Pacific are keeping San Francisco temperatures near seasonal norms, with National Weather Service forecasts showing Thursday highs in the 60s to mid-70s under partly cloudy skies.** The layer, measured around 1,000–1,700 feet deep in recent soundings, promotes stratus development overnight that mixes out gradually during the day, limiting solar heating and capping the daily maximum. Current model consensus and recent observations indicate no strong offshore flow or ridging to override this pattern, producing the tight clustering of market-implied odds around 72–75°F. Minor variations in exact clearing time, local wind gusts of 5–15 mph, and microclimate differences across the city create the narrow spread among leading bins, while historical August averages near 70°F provide context for the subdued outlook. Updated NHC/NOAA guidance or morning observations could shift the distribution ahead of resolution.