Recent National Weather Service guidance and ensemble model runs indicate a moderately compressed marine layer and light onshore flow supporting a San Francisco high near 70–72°F on August 19, aligning with the market’s tight clustering around the 70–71°F and 72–73°F brackets. Shallower stratus overnight has permitted greater daytime insolation than earlier in the week, while persistent sea-breeze circulation continues to limit further warming. Historical August climatology at KSFO shows a 67–70°F mean high, so current conditions sit slightly above average yet remain well below heat-wave thresholds. Traders are monitoring the next NHC and local sounding updates for any late compression or strengthening of the marine inversion that could shift the outcome by a degree or two.