Recent National Weather Service guidance and ensemble model runs indicate a typical late-September marine layer setup for San Francisco, with morning low clouds and onshore flow likely limiting afternoon heating. Highs have ranged from the mid-60s to low-70s in recent days following an early-month heat spike, and forecasters currently project a peak near 68–72 °F on the 17th depending on the exact timing of any clearing and wind strength. This narrow range explains the near-even market split between the 70–71 °F and 72–73 °F bins, with the slight edge to the former reflecting modest model consensus around modest warming under partly sunny conditions. Historical September averages near 71 °F provide additional context, though coastal variability keeps lower or higher outcomes possible if the marine influence strengthens or weakens unexpectedly.