**Widespread cloud cover and thunderstorms expected across the Mexico City valley on August 24 are the main factors capping daytime heating, with official forecasts pointing to a maximum near 20–21°C.** Persistent monsoon moisture and orographic effects from the surrounding mountains sustain overcast skies and scattered rain, limiting solar insolation and surface warming at the city’s 2,240-meter elevation. Recent model runs from sources including the National Meteorological Service and international ensembles show highs clustered between 18–22°C, reflecting typical late-summer variability rather than extreme anomalies. Traders have concentrated implied probability on 20°C and 21°C because small differences in cloud timing or convective timing can shift the observed peak by a degree or two, while historical August maxima in the basin rarely exceed 23°C under similar synoptic patterns. Updated regional guidance and station observations tomorrow will provide the final resolution data.