National Weather Service forecasts point to a high near 68°F in San Francisco on August 20, reflecting a compressed marine layer and persistent onshore flow that sustains low stratus clouds and limits afternoon solar heating. This pattern keeps readings at or below the lower end of August climatology around 70–73°F at downtown and airport sites. Trader consensus clusters on the 68–69°F and 70–71°F bins because model guidance shows only minor differences in inversion strength or the precise timing of any partial clearing; stronger or more prolonged stratus favors the cooler outcome while a brief afternoon break could nudge readings into the low 70s. No offshore winds or anomalous ridging have developed to alter the setup.