**NWS forecasts for San Francisco on August 13, 2026, center on a mostly cloudy high near 66°F amid a cooling trend driven by a persistent marine layer and southwesterly flow.** This aligns with the market's tight clustering around 66–69°F outcomes, reflecting trader consensus on modest onshore advection of cooler Pacific air that limits daytime warming. Model guidance shows limited spread, with 925–850 mb temperatures remaining below seasonal norms and only modest diurnal recovery expected under partial clearing. Key variables differentiating the 66–67°F versus 68–69°F bins include the exact timing and depth of the marine layer, wind speeds near 10–15 mph, and any late-day sun breaks that could add 1–2°F. Historical August highs average ~70°F, so current conditions represent a modest negative anomaly consistent with the troughing pattern noted in recent NWS discussions. Updated model runs and afternoon observations will provide the final resolution data.