**Forecast uncertainty around afternoon convection and cloud cover is the main driver keeping trader probabilities clustered tightly around 23–24°C for Mexico City’s August 22 high.** Official guidance and ensemble models show a mostly cloudy day with scattered thunderstorms possible after midday, which would limit solar heating at the city’s 2,240 m elevation and cap the peak near 22–24 °C (roughly 72–75 °F). Stronger or earlier storms could suppress readings to 22 °C or below, while delayed or lighter precipitation would allow brief clearing and push the maximum to 25 °C. Recent days have featured similar patterns, with observed highs fluctuating 1–2 °C day-to-day depending on storm timing; historical August maxima average near 23–24 °C under comparable moisture and pressure setups. Updated model runs and afternoon radar trends through the evening of August 21 will likely decide whether the market tilts toward the 23 °C or 24 °C outcome.