Traders see roughly equal implied probabilities for a Jeddah minimum of 29–31 °C on 21 August 2026 because official forecasts and ensemble models cluster tightly around the long-term August average low of 30 °C. The decisive variables are the strength of nocturnal radiative cooling under persistently high Red Sea humidity (often 55–65 %), which limits temperature drop, versus any increase in low-level wind or thin cloud that could enhance mixing and keep readings nearer 31–32 °C. Local factors such as the urban heat-island effect and the timing of the land–sea breeze further narrow the range, while subsidence typical of the Arabian heat low suppresses major deviations. With resolution hours away, small differences in the latest model runs or observational updates can still shift the final recorded minimum among the leading bins.