Recent forecast guidance from global and regional models points to overnight lows in São Paulo on October 9 near 18–20 °C, reflecting springtime warming under generally stable subtropical high pressure with light winds and moderate humidity that limits strong radiative cooling. Trader sentiment remains closely balanced because small differences in the timing or strength of any weak southern cold-air intrusion, or variations in cloud cover that alter nocturnal heat retention, could shift the minimum across key thresholds. Ensemble spreads in GFS and ECMWF runs highlight this uncertainty, with some members allowing brief dips toward 16–17 °C if drier air arrives earlier, while others keep readings above 21 °C under continued mild flow. Updated model cycles and official INMET guidance expected in the next 24–48 hours will likely refine these probabilities ahead of market resolution.