**Forecast uncertainty across models centers on overnight radiative cooling under variable cloud cover and scattered rain during Mexico City's highland rainy season.** Official Mexican forecasts (CONAGUA/SMN) and several global models project a minimum of 12–14°C for August 31, consistent with the 13°C climatological average for late August at 2,240 m elevation, where clear skies allow stronger cooling but frequent afternoon convection often leaves residual moisture and clouds that limit overnight drops. Recent model runs show spread in low-level moisture and wind patterns, with lighter winds favoring slightly cooler readings near 12°C while increased cloudiness or showers could hold temperatures near 14–15°C. The tightly clustered market odds around 12–15°C reflect this genuine short-range forecast dispersion rather than any atypical event, as traders weigh the balance between typical seasonal cooling and the moderating influence of ongoing monsoon moisture. New model updates and official morning briefings on the 31st will likely refine the exact minimum before resolution.