Recent observational data from National Weather Service stations in Chicago indicate a minimum temperature settling in the low 50s°F on September 14, aligning with the market's strong 87.5% implied probability for the 52-53°F bin. Mid-September climatology typically features overnight lows near 55-60°F, but a passing high-pressure system and clear skies promoted enhanced radiational cooling, lowering readings below seasonal averages. Model consensus from the prior 48 hours showed limited spread around this outcome, with minimal uncertainty from wind or cloud cover shifts. Upcoming official daily summaries will confirm the exact reading for market resolution, though trader positioning already reflects high confidence in this narrow range based on verified station data.