Current forecasts from the National Weather Service and major models indicate a low temperature in the mid-70s°F for Chicago on August 31, driven by a warm, humid air mass with southerly flow and partial cloud cover that limits overnight radiational cooling. Highs near 89°F the prior day and persistent moisture maintain elevated minimums, consistent with recent August trends showing above-average lows. Trader probabilities cluster tightly around 72–77°F bins because small differences in cloud timing or wind speed could shift the exact minimum by a degree or two, while historical August 31 averages near 64°F highlight the unusual warmth this year. New model runs and evening observations will refine these near-term estimates.