**Forecast models from sources including the China Meteorological Administration, international agencies like the Met Office, and private providers such as WeatherBug and LUFT TIME converge on a daily minimum of 21–24°C for Shanghai on September 22, 2026, with most guidance centering on 22–24°C.** This narrow range and slight model spread explain the near-even split between 23°C and 24°C (each at 37.5% implied probability), followed by 22°C at 14.5%. Key drivers include light northeast to east winds under generally stable high pressure, which limit mixing and allow modest nocturnal radiative cooling after daytime highs near 29–30°C. Overnight cloud cover and humidity levels around 70–85% moderate temperature drops, while Shanghai’s urban heat island effect adds a small warming bias to official station readings. Minor differences in predicted cloud thickness, wind speed (typically 2–7 km/h), and boundary-layer moisture between runs such as GFS and regional models create the uncertainty separating the top outcomes. No significant weather systems or rapid changes are expected in the next 24–48 hours, keeping the distribution tightly clustered around these values. Updated model runs and official briefings closer to the overnight period will likely refine the exact minimum before market resolution.