Recent forecast model consensus and upper-level ridging over the eastern Pacific are the main drivers behind the closely matched probabilities for 86–91°F peaks in San Francisco on October 3. Subsidence has compressed the marine layer, allowing northeast to northwest offshore flow to advect warmer, drier air while suppressing coastal stratus and enabling greater daytime heating than the early-October climatological average of 71–72°F. Ensemble guidance shows modest spread in boundary-layer mixing and exact wind timing, which explains why the 88–89°F and 86–87°F bins hold slight edges while 90–91°F remains competitive; any slower marine-layer erosion or stronger afternoon sea breeze could cap readings near 84–85°F. Official NWS and private-model runs continue to trend toward sunny conditions with highs in the upper 70s to low 80s at downtown stations, leaving room for last-minute adjustments before resolution.