Recent official forecasts from Environment Canada and supporting model guidance indicate a mix of sun and cloud for Toronto on September 30, with a daytime high near 22°C and overnight low around 15°C under moderate southwesterly flow. This places the expected daily minimum squarely in the middle bins, yet the near-even market split between 9°C or below and 19°C or higher reflects lingering uncertainty in short-range guidance. Key differentiating factors include the strength and timing of any incoming frontal boundary, which could enhance northerly advection and radiative cooling under clearer skies or maintain milder conditions via cloud cover and southerly return flow. Historical late-September variability in the region, with typical overnight lows near 12–14°C, underscores how small shifts in 850-hPa temperatures or boundary-layer moisture can swing the minimum several degrees. Traders will monitor the next ECMWF and GFS runs plus updated Environment Canada briefings for refinements ahead of resolution.