The market-implied odds favor 72-73°F as the leading outcome for San Francisco’s July 20 high, reflecting trader consensus on a moderately suppressed marine layer that permits modest afternoon warming under persistent high pressure. The city’s characteristic summer temperature inversion—driven by cool Pacific waters and the California Current—typically caps highs near the 68°F July climatological mean, yet recent model runs show reduced onshore flow and a shallower layer depth allowing peaks in the low 70s. Stronger La Niña conditions this season have reinforced the marine layer overall, creating uncertainty around exact timing of any sea-breeze surge or fog clearance that could shift the high by a degree or two. National Weather Service updates through the evening of July 19 will refine these thresholds ahead of resolution.