Recent forecast model consensus from sources including GFS and regional meteorological guidance indicates overnight lows near 18–19°C in São Paulo on September 26 under predominantly clear skies and light variable winds. This positions 17–19°C outcomes as scientifically favored, though the market-implied probability spread reflects model uncertainty in boundary-layer mixing, urban heat retention, and subtle shifts in steering flow that could nudge the minimum by 1–2°C either way. Warmer-than-climatological September conditions have already elevated baseline temperatures, supporting the elevated odds on 24°C or higher while limiting downside risk below 16°C. Updated model runs and official observations overnight will refine resolution criteria for this single-day minimum.