Official National Weather Service observations from Chicago O’Hare International Airport recorded a daily high temperature of 64–65°F on May 22, aligning with the market’s near-certain consensus for that outcome. Persistent northeast onshore flow from Lake Michigan suppressed warming beneath a cool air mass, keeping readings several degrees below the mid-May climatological average of roughly 73°F. Ensemble model guidance and surface analyses throughout the period consistently projected limited diurnal heating under mostly cloudy skies, with no late-day clearing or wind shift sufficient to reach 66°F. This observational confirmation from authoritative monitoring stations resolves the market while illustrating how lake-effect moderation and regional synoptic patterns can anchor temperatures within narrow daily ranges.