Recent forecasts for Beijing on September 13 indicate clear skies and light northwesterly winds under a stable high-pressure system, favoring strong overnight radiative cooling that typically produces minimum temperatures in the mid-teens Celsius. Multiple models converge on lows around 16–17 °C, consistent with September climatology of roughly 16.7 °C, though slight differences in boundary-layer mixing and dew-point depression explain the tight clustering between 15 °C and 17 °C outcomes. Higher-probability bins near 15–16 °C reflect trader weighting of the most consistent ensemble guidance, while the 21 °C+ option captures residual uncertainty from any unexpected warm advection or model bias. Updated runs from agencies such as the China Meteorological Administration or global ensembles will likely refine the exact minimum before resolution.