Recent National Weather Service and model guidance point to an overnight low for Chicago on August 25 near or slightly below the 64°F climatological normal, with trader sentiment concentrated on the 56–61°F range amid closely matched probabilities. Key differentiating factors include variable radiational cooling under partly to mostly clear skies, light wind speeds that limit boundary-layer mixing, and dew-point temperatures around 55–60°F that support modest cooling before sunrise. A weak frontal passage or subtle subsidence from upstream high pressure may suppress cloud cover and enhance the drop, while any increase in southerly flow or lingering moisture could cap the minimum a few degrees higher. Ensemble spreads in short-range guidance create the narrow probability gaps among these bins, with resolution hinging on final observational data from O’Hare or Midway.