Official National Weather Service observations at Chicago O’Hare recorded a maximum of 73°F on October 4, 2026, under sunny skies and light northwest winds, exceeding the 1991–2020 normal of 68°F by five degrees. Pre-event model consensus and real-time forecasts consistently projected highs in the low to mid-70s, aligning with the final reading and supporting the market’s near-certain 72–73°F outcome. This reflects aggregated trader assessment of surface observations, upper-air patterns, and climatological baselines rather than forecasts. A realistic shift would require an official station revision or use of an alternate reporting site, though both remain improbable given consistent data across networks.