Recent National Weather Service and ensemble model guidance points to overnight lows in Chicago on August 29 falling primarily in the mid-to-upper 60s, driven by increasing cloud cover and light southwesterly winds that limit radiational cooling. These conditions contrast with clearer, calmer setups that could allow temperatures to dip toward 62–63°F. The closely matched market probabilities across 62–67°F bins reflect genuine uncertainty in short-range forecasts, as differing model runs diverge on the timing and extent of cloudiness ahead of a weak frontal boundary. Historical late-August climatology shows average overnight minima near 65°F, providing context for the current range, while updated model outputs expected overnight will likely refine the consensus ahead of resolution.