Trader sentiment for Mexico City's October 13 minimum temperature shows a tight contest between an implied 14°C outcome and lower readings around 8–11°C, driven by variable overnight radiational cooling in the high-elevation Valley of Mexico. Clear skies and light winds under a post-frontal air mass can enhance surface heat loss, while scattered showers and increased cloud cover moderate the drop. Official observations from networks like the Servicio Meteorológico Nacional highlight how local basin effects and elevation create 3–6°C spreads between forecast models. With the event now past, resolution hinges on verified station data distinguishing between typical early-October minima near 13°C and sharper cooling episodes.