Official National Weather Service observations from Chicago stations, including O’Hare, recorded a daily maximum of 76–77°F on September 10, 2026, locking in the market’s near-100% consensus on that bin. Pre-event model guidance and local forecasts had projected highs near 80°F under partly sunny skies with moderating humidity, yet actual afternoon temperatures peaked slightly below those expectations amid persistent cloud cover and lighter winds. This outcome aligns closely with the 1991–2020 climatological average high of 78°F for the date while remaining well below historical extremes. Only an unreported station discrepancy or post-verification adjustment could realistically alter the result, though such revisions are rare once preliminary data are confirmed.