Jeddah's August 4 maximum temperature market is led by the 40°C-or-higher outcome at 38.5% implied probability because National Center of Meteorology seasonal guidance projects above-normal temperatures across western Saudi Arabia through October, with potential anomalies of 1–2°C driven by persistent high-pressure patterns and Red Sea heat advection. Short-range ensemble and regional models currently cluster daily highs near 38–41°C under mostly clear skies, consistent with Jeddah's climatological August peak where insolation and low-level humidity routinely push afternoon readings into the upper 30s to low 40s. Modest forecast spread arises from uncertainty in exact timing of peak heating and any subtle moisture intrusions that could cap temperatures, keeping the 38°C bin at 26% and leaving room for revision as new model runs and NCM updates arrive before resolution.