Current global forecast models place Jeddah’s May 18 daytime maximum near 45 °C, supported by a strong subtropical ridge delivering intense solar insolation, light northwesterly winds that suppress sea-breeze cooling, and low-level humidity that elevates the heat index along the Red Sea coast. Historical May maxima average 37–39 °C, yet episodic heat events push readings into the mid-40s when boundary-layer mixing strengthens and cloud cover remains minimal; the closely bunched 44–46 °C brackets reflect uncertainty in afternoon dew-point recovery and exact timing of any weak onshore flow. Ensemble guidance from GFS and ECMWF will sharpen these distinctions over the next 48 hours, with any upward revision in surface temperatures favoring the 48 °C-or-higher tail.