Current forecasts from GFS and regional models indicate a mild overnight low near 18–19°C for São Paulo on September 28, driven by persistent warm advection, light easterly winds, and partial cloud cover that limits radiative cooling. This places the outcome well above the September climatological minimum of ~12°C and aligns with the recent warmer-than-average pattern observed through late September 2026. Market-implied odds remain nearly even between the 23°C+ and 13°C-or-below bins because traders weigh model spread in boundary-layer moisture and any late-day frontal approach that could alter the minimum by 2–3°C. Updated runs from official agencies in the next 24–48 hours will refine the exact threshold, particularly if dew-point depressions tighten overnight.