Official National Weather Service observations at Chicago Midway Airport recorded a daily maximum of 80°F on September 7, 2026, one degree above the 1991–2020 normal and well below historical records near 100°F. This aligns with post-heat-wave cooling after early-September highs near 96°F, driven by a shift to northerly flow and reduced insolation. Market-implied odds reflect these verified measurements rather than forecasts, with traders assigning near-certainty to the 80–81°F bin. Only minor station-to-station variations, such as between Midway and O’Hare, or unreported microclimate effects could realistically alter the recorded high enough to challenge resolution.