**Current forecasts from the National Weather Service and major models indicate Chicago’s October 4 low will most likely fall in the upper 40s to low 50s under partly to mostly clear skies and moderate northwest flow following a weak frontal passage.** This pattern favors radiative cooling overnight without strong cold advection, aligning with the climatological average low near 51°F. A reading of 41°F or below would require either a sharper post-frontal push of drier, colder air or unusually efficient radiational cooling under calm, clear conditions rarely seen this early in October. Conversely, a low of 60°F or higher would need persistent cloud cover or a warmer southerly flow that suppresses nocturnal temperature drops—both inconsistent with the current steering pattern and ensemble guidance. The closely matched market-implied odds on the extremes reflect lingering uncertainty in exact boundary-layer mixing and cloud timing rather than divergent model solutions.