Official National Weather Service observations at Chicago O'Hare recorded a daily maximum of 78°F on October 11, 2026—13°F above the 1991–2020 normal of 65°F—driving the market's near-certain alignment with the 78–79°F bin. This unseasonable warmth stemmed from persistent southerly flow and dry conditions that limited cooling, consistent with pre-event forecasts highlighting mid-to-upper 70s highs amid clear skies and light winds. NOAA climatological reports confirm no precipitation or significant cloud cover altered the peak reading. While model consensus and station data leave little room for revision, traders recognize that rare post-event adjustments to official records or use of an alternate station like Midway could theoretically shift resolution, though historical precedent shows such changes are minimal for temperature maxima.