Trader consensus clusters around 68–71°F for San Francisco’s August 20 high because the marine layer depth and onshore flow remain the dominant controls on afternoon warming. A persistent inversion capped by the Pacific high keeps cool, moist air from the California Current in place, limiting insolation and holding maxima near the seasonal 67°F norm; however, any shallowing of the layer or slight offshore wind shift could allow partial clearing and push readings into the low 70s. Latest model guidance shows modest variability in layer height and wind speed through the morning, creating the tight spread between the 68–69°F and 70–71°F bins while suppressing odds for extremes. Official National Weather Service forecasts emphasize continued stratus and moderate westerlies, yet small changes in these parameters can shift peak temperature by 3–5°F in this coastal microclimate.