The market's near-certain pricing on a 17°C low for Toronto on September 13 reflects official meteorological observations confirming that minimum overnight temperature, consistent with National Weather Service and Environment Canada station data under partly cloudy conditions with light northwest winds. Forecasts from global models such as the GFS accurately anticipated this value, aligning with seasonal norms where mid-September lows typically range 14–16°C in the region. Trader consensus draws on real-time surface observations rather than models alone, reducing uncertainty as the date concluded. A realistic challenge would require a post-analysis revision from the primary reporting station or a resolution rule emphasizing a secondary site with a notably different reading, though such discrepancies remain rare for urban temperature markets.