Forecast models from agencies like the Met Office and local meteorological services indicate a peak temperature near 36–37°C in Jeddah on September 21, driven by strong September solar insolation under mostly clear skies, light to moderate westerly winds, and typical Red Sea humidity levels that limit overnight cooling but allow daytime heating to near seasonal norms around 36–37°C. Slight divergences in model runs—particularly on exact timing of peak winds or minor high-cloud effects—create genuine uncertainty between 36°C and 38°C outcomes, consistent with the closely matched market-implied odds of 38% for 37°C, 28% for 36°C, and 21% for 38°C. Historical September maxima in the city often fall in this narrow range, with resolution depending on the official daily high reported by monitoring stations.