**Official National Weather Service observations from Chicago O’Hare International Airport recorded a daily maximum of 72°F on September 27, 2026, reached at 1:52 p.m. CDT.** This places the high squarely in the 72-73°F bin that now carries 100% market-implied probability. The value sits only 1°F above the 1991-2020 normal high of 71°F and aligns with cooler-than-average late-September conditions driven by northerly flow and limited insolation under partly cloudy skies. Multiple nearby stations reported highs between 70-73°F, reinforcing the consensus. Because the date has passed and preliminary climatological summaries have been issued, the outcome is effectively settled unless the National Weather Service issues a formal revision. Realistic challenges are limited to post-publication data corrections or an alternate station definition, both of which have historically been rare for daily temperature markets.