The market's near-certain 21°C outcome reflects verified observations from official stations such as Toronto Pearson, where the daily maximum reached exactly that level under mostly sunny, mild conditions with light northerly winds. This aligns closely with the 1991–2020 climatological average high of 19.9°C for September 25 and pre-event forecasts from Environment and Climate Change Canada projecting 19–20°C. Late-summer atmospheric patterns featuring stable high pressure and dry air prevented any warmer intrusions or significant warming aloft. Only an unexpected revision in official reporting or station-specific microclimate differences could alter resolution, though such adjustments remain rare once preliminary data are confirmed.