**A heat dome positioned south of the region is sustaining elevated temperatures and humidity into early September, pushing forecast overnight lows for Chicago on September 1 into the mid-to-upper 70s°F.** Multiple short-range models and National Weather Service guidance indicate highs near 90–94°F with dew points in the 70s, limiting nocturnal radiative cooling and keeping minimum temperatures well above the long-term average of ~64°F. Southwest flow and variable cloud cover or scattered showers further reduce the potential for sharp drops, while any clearing could allow slightly more cooling. The closely matched market odds—particularly the 29.5% on both 67°F or below and 86°F or higher—reflect residual uncertainty in how much the heat and moisture will suppress the daily minimum versus any late-day cooling from convection or wind shifts. Mid-range buckets around 74–77°F capture the central tendency of current ensemble guidance, but traders weigh the risk of model spread in boundary-layer mixing and precipitation timing. With resolution imminent, updates to dew point forecasts and cloud trends from NOAA/NWS will be the key drivers of any final shifts in implied probabilities.