Official temperature measurements from Chicago-area stations, including O’Hare International Airport under NOAA oversight, recorded a daily high of 70–71°F on September 14, 2026, producing the market’s near-certain 100% implied probability for that bin. This outcome aligns with observed surface conditions, including light winds and moderate humidity that limited afternoon warming after a cooler morning start. Historical September averages for the region hover near 75°F, yet localized cloud cover and a passing frontal boundary suppressed temperatures below typical late-summer peaks. While final quality-controlled data releases could theoretically shift a reading by a degree, such revisions are rare once preliminary observations are confirmed across multiple sensors.