**Persistent cloud cover, widespread rain, and thunderstorm activity are the dominant factors capping daytime heating in Mexico City today.** Forecasts from multiple sources converge on a maximum near 19–21 °C, aligning with the market’s tight clustering around the 20–22 °C outcomes (combined >75 % implied probability). Overcast skies and precipitation reduce incoming solar radiation, while light northerly winds and high relative humidity (often >70 %) further limit temperature rise at the city’s ~2,240 m elevation on the Mexican Plateau. This pattern reflects the active phase of the regional wet season, when afternoon convection frequently develops and suppresses peaks below the long-term August average high of ~23–24 °C. Model runs show only modest spread in timing and intensity of rain, keeping the distribution of possible maxima narrow and centered in the low 20s °C. Traders are therefore pricing the scientific consensus that today’s conditions will prevent both significant warming above 23 °C and sharp cooling below 19 °C, with resolution hinging on the precise timing of any clearing or heaviest rainfall.