Forecast models from the National Weather Service and private sources indicate overnight lows in Chicago on October 4 centered in the upper 40s to mid-50s Fahrenheit, driven by northwest winds advecting cooler continental air after a mild Saturday and variable cloud cover that modulates radiative cooling rates. This places the outcome near the historical average low of 50.9°F while creating tight clustering around mid-range bins as traders weigh steering patterns, dewpoint trends, and lake moderation effects that could shift minimums by several degrees. High implied probabilities on sub-41°F or 60°F+ extremes reflect genuine short-term model spread in boundary-layer mixing and any late-day frontal timing rather than strong consensus, with resolution hinging on official Chicago O'Hare observations during the overnight window.