**Recent forecast models indicate overnight lows in Mexico City on September 6 around 13–15°C, driven by cloud cover, rain, and thunderstorms expected that day.** High-altitude radiative cooling at roughly 2,240 meters normally allows temperatures to drop sharply after sunset, but increased moisture and precipitation during the peak of the rainy season moderate this effect by trapping heat and reducing clear-sky heat loss. Multiple sources, including Yr.no hourly data and agency outlooks, show early-morning readings bottoming near 14°C under mostly cloudy skies with rain totals projected at 4–15 mm. This aligns with the market’s leading 17°C-or-higher outcome at 44.5% implied probability, reflecting trader consensus that the low will stay relatively mild. Lower-probability bins such as 12°C or 7°C-or-below capture residual model uncertainty around exact rainfall timing and intensity, which could allow brief additional cooling if breaks in cloud cover occur. Historical September averages near 10–13°C provide context, but current synoptic conditions favor the warmer end of the distribution. Traders will watch the final 48-hour model runs and official Servicio Meteorológico Nacional guidance for any late shifts in steering flow or storm coverage before resolution.