Current forecasts from regional models place Jeddah’s September 11 maximum near 36–38 °C, with the market split almost evenly between 37 °C and 38 °C or higher because small differences in timing of peak heating and boundary-layer mixing can shift the daily high by 1–2 °C. Persistent subtropical high pressure and strong solar insolation near the autumnal equinox drive daytime warming across the Red Sea coastal plain, while light westerly winds and moderate humidity (50–60 %) limit evaporative cooling and allow temperatures to climb steadily after sunrise. Recent early-September observations have already reached 38 °C, providing a warm baseline, yet ensemble spreads in GFS and ECMWF runs still show a 1–2 °C range for the 11th depending on subtle changes in sea-breeze onset and low-level moisture. Updated model cycles and official Saudi Met guidance later today will be the next key inputs for traders assessing whether the peak settles at 37 °C or edges into the 38 °C-plus bin.