**Forecast models for Mexico City on September 9, 2026, currently point to an overnight minimum near 12–14 °C under persistent cloud cover and scattered rain.** Mexico City’s high elevation (~2,240 m) promotes efficient nocturnal radiative cooling when skies clear, but the active rainy season—driven by low-level moisture, troughs, and monsoon influences—has produced widespread cloudiness that limits heat loss. Recent observations show daily minima clustered around 13–14 °C, with light winds and high humidity further moderating extremes. Official Servicio Meteorológico Nacional guidance and multiple numerical models (including GEM and ECMWF runs) indicate continued overcast conditions and showers through the night of September 8–9, which tend to hold temperatures in the mid-teens rather than allowing sharp drops below 10 °C or rapid warming above 16 °C. The closely matched market-implied probabilities for 16 °C or higher (42 %) versus 6 °C or below (41.5 %) reflect uncertainty around exactly how much clearing or additional moisture arrives overnight. Key variables include the timing and intensity of any breaks in cloud cover, which control the strength of longwave radiative cooling, and subtle shifts in steering flow that could alter dew-point temperatures. Updated model runs and official forecasts issued in the next 12–24 hours will likely narrow the range and move the market-implied odds accordingly.