Recent observational data and forecast models from agencies like Mexico's Servicio Meteorológico Nacional indicate Mexico City's September 4 overnight low settled near 12–13°C amid typical high-elevation radiative cooling at roughly 2,240 meters, moderate cloud cover limiting further drops, and light winds reducing mixing. September climatology shows average minima around 10°C with frequent 12–14°C readings during the rainy season transition, supporting the market's heavy weighting toward 12°C. The notable share for 7°C or below reflects residual uncertainty in localized urban heat island effects versus clear-sky episodes or model spread in temperature inversions. Updated surface observations and station reports will resolve the exact threshold once fully processed.