Forecast models for Mexico City on August 30 show overnight lows likely ranging 11–14 °C, with trader-implied probabilities clustered tightly across those bins because of small differences in expected radiative cooling under variable cloud cover and light rain. At 2,240 m elevation, the city experiences efficient nocturnal heat loss when skies clear, but afternoon thunderstorms and lingering low-level moisture from the ongoing rainy season suppress temperature drops by trapping longwave radiation. Recent GFS and ECMWF runs differ slightly on the timing of clearing after evening showers and on boundary-layer wind speeds, directly affecting whether the minimum registers near 11 °C or holds closer to 14 °C. Historical August climatology places typical lows around 12–13 °C, providing a narrow baseline that keeps multiple outcomes competitive until final observational data resolve the market.