**Official National Weather Service observations from Chicago O’Hare confirm a maximum temperature of 73°F on October 8, 2026, reached at 1:48 PM CDT under clear skies and light winds.** This value sits 7°F above the 1991–2020 normal high of 66°F and aligns precisely with the market’s dominant 72–73°F outcome. Real-time surface data, including hourly readings peaking near 22–23°C (72–73°F) across the metro area, drove trader consensus toward near-certainty once the calendar day closed. Minor station-to-station differences (e.g., 68–76°F reported elsewhere) remain within typical urban heat-island and siting variability, but the ORD climatological summary serves as the authoritative reference for resolution. Only an unprecedented post-observation revision or non-standard measurement protocol could alter the outcome at this stage.