Recent National Weather Service forecasts and ensemble guidance indicate southerly flow and increasing cloud cover will limit overnight radiational cooling across Chicago on August 30, keeping minimum temperatures in the low-to-mid 70s. Persistent warm advection ahead of a building ridge, combined with dew points near 63–67 °F, supports this elevated floor relative to the 1991–2020 climatological average low of 64 °F. Model spread centers on the timing and coverage of any light showers or thicker clouds, which could nudge the actual minimum a degree or two higher or lower. With the market-implied probabilities tightly clustered between the 66–75 °F bins, traders are pricing in this narrow but genuine forecast uncertainty ahead of the final NWS verification at official stations.