Current short-range forecast models from global and European ensembles indicate a maximum near 21°C for Istanbul on May 19, aligning with the tightly clustered market-implied probabilities around 20–22°C. This range reflects the city’s mid-May climatological baseline of 20–23°C, moderated by the Bosphorus marine influence that often caps afternoon warming through sea-breeze advection. Small differences among leading outcomes hinge on model spread in cloud-cover timing and low-level wind direction, which can shift peak readings by 1–2°C. As resolution nears, updated model runs and official observations from Istanbul Airport will refine these probabilities, highlighting the inherent uncertainty in diurnal temperature forecasts under transitional spring conditions.