Recent forecast model runs and observational updates from Environment Canada and NOAA created tight uncertainty between 7°C and 8°C as the likely overnight minimum in Toronto on October 4. Variable cloud cover, light winds, and a moderating air mass from the southwest limited radiative cooling, while localized showers and humidity levels influenced how sharply temperatures fell after sunset. Historical climatology for early October shows an average low near 10°C, but the specific steering pattern and boundary-layer conditions on the day pushed trader consensus toward the lower end of typical ranges. New surface observations and refined model ensembles released in the final 24 hours before resolution kept the two leading outcomes nearly even, reflecting genuine ambiguity in the precise threshold.