Recent National Weather Service guidance and ensemble model runs show a transitional pattern over Chicago, with northwest winds shifting to southerly flow ahead of a warm front. This setup produces overnight lows for September 14 most likely in the mid-50s to mid-60s, depending on cloud cover and sustained wind speeds that limit radiative cooling. Breezy conditions and increasing humidity reduce the chance of sharp drops below 50 °F, while partial clearing early in the period supports the market's elevated probability on 68 °F or higher. Historical mid-September normals near 59 °F provide context, yet the tight clustering of probabilities across bins reflects ongoing divergence among short-range guidance on exact minimum timing and boundary-layer mixing. Updated model runs and NWS forecast discussions expected overnight will clarify resolution thresholds.