Official National Weather Service observations at Chicago O’Hare recorded a maximum of 69°F on October 3, 2026, reached near 3 PM CDT under clear skies and light southerly flow. This direct measurement from calibrated instruments at the primary reference station aligns with nearby reports from Midway (70°F) and Rockford (69°F), confirming the value within the 68-69°F bin and driving the market’s near-certain consensus. Historical averages for the date hover near 69°F, so conditions matched climatology without notable anomalies. A realistic challenge would require an official data revision or a shift to an alternate station definition, both uncommon once preliminary climatological reports are issued.