Official observations from National Weather Service stations in the Chicago area recorded a daily maximum of 84–85°F on September 8, 2026, well above the 1991–2020 climatological normal of 78–79°F but short of historical extremes near 96°F. This verified reading, drawn from calibrated surface stations and consistent with nearby reports of mid-80s highs under sunny conditions, anchors the market-implied probability at 100% for the 84–85°F bin. Minor station-to-station variations or post-hoc quality-control adjustments remain the only realistic paths to a different resolution, though such changes are rare once preliminary climatological summaries are issued.