**Forecast models indicate a typical late-September minimum near 27–29°C in Jeddah, driven by persistent marine influence from the warm Red Sea (surface temperatures ~32°C) and high humidity that limits nocturnal radiative cooling.** Light northwesterly winds and clear skies under stable high pressure favor a modest diurnal range, with the daily low occurring around dawn before sea-breeze strengthening. Historical September averages for the city show overnight lows in the mid-to-upper 20s °C, consistent with current ECMWF and GFS guidance showing little day-to-day change through the 27th. Trader sentiment remains split between the sub-24 °C and 34 °C+ tails because small forecast shifts in humidity, wind speed, or cloud cover near sunrise can move the exact minimum across common resolution thresholds; fresh model runs and official Saudi observations will provide the next key updates.