Traders assign the highest probability to a San Francisco high of 72–75°F today because persistent marine layer stratus and moderate onshore flow from the Pacific are limiting daytime heating, consistent with National Weather Service ensemble guidance. The near-even split between the 72–73°F and 74–75°F bins reflects uncertainty in afternoon clearing timing and boundary-layer mixing; stronger sea breezes or lingering fog would cap readings near the lower end, while brief sun exposure and light winds could push temperatures one to two degrees higher via the urban heat island. This range aligns with typical early-August climatology for the city, where coastal influences keep extremes rare.