Trader consensus around 70–73°F for San Francisco’s July 28 high reflects the dominant influence of the marine layer and persistent onshore flow from the Pacific, which typically caps afternoon temperatures near the 68–72°F July climatological average at the official KSFO station. NOAA and NWS guidance show modest warming potential from a building high-pressure ridge, but model spreads in cloud-clearing timing and boundary-layer mixing create the tight clustering across 68–73°F bins. Stronger winds or deeper fog would favor the lower outcomes, while any offshore component could briefly push readings toward 74°F. Resolution hinges on the official maximum recorded at the airport, with final forecast updates expected overnight.