Recent National Weather Service and model guidance indicate Chicago's overnight low on August 25 will likely settle near 60–65°F, below the 1991–2020 normal of 64°F at O'Hare, as a northwest flow and clearer skies promote radiational cooling under light winds. Ensemble spreads highlight modest uncertainty in boundary-layer mixing and dewpoint trends, keeping the 58–59°F and 56–57°F bins tightly matched at the front of trader positioning. Lake Michigan's moderating influence and the absence of strong warm advection further cap upside risk, while any late-day cloud cover or slight wind shift could push readings toward the 62–63°F range. Updated short-range model runs and the evening NWS forecast discussion will provide the next key data points for refining these probabilities ahead of the overnight minimum.