Forecast models from the China Meteorological Administration and global ensembles show tight clustering around 17–18°C for Jinan’s overnight low on August 31, producing the near-even market split. Subtle differences in predicted cloud cover, boundary-layer humidity, and surface wind speeds under a weak high-pressure ridge determine whether radiative cooling reaches 16°C or stalls near 19°C. Late-summer monsoon retreat and typical diurnal ranges of 10–12°C provide the baseline, while urban heat-island effects in the city center add a small upward bias. Final model runs and local observations tonight will resolve the narrow spread before the market closes.