Recent ensemble forecasts from the ECMWF and GFS models project a highest temperature in Istanbul on May 18 near the seasonal average of 20–22 °C, with modest uncertainty arising from variable cloud cover and Bosphorus marine influence that can suppress afternoon warming by 1–2 °C. A building high-pressure ridge over the eastern Mediterranean favors light southerly flow that could push readings to 22 °C if skies remain mostly clear, while increased low-level moisture or stronger northerly winds would cap the peak at 19–20 °C. These closely matched market-implied odds reflect the narrow spread in current guidance, with final resolution determined by official observations at Istanbul Airport; updated model runs on May 17 will likely tighten the range before the daily maximum is recorded.