Forecast models for Istanbul on May 18 indicate a typical late-spring pattern, with daytime highs expected near the long-term average of 21°C under variable cloud cover and light northerly winds. The closely bunched probabilities around 19–22°C reflect minor divergences among ensemble runs from agencies like ECMWF and GFS, primarily tied to uncertainties in afternoon sea-breeze strength from the Bosphorus and potential thin high clouds that could trim peak readings by 1–2°C. No strong warm or cold advection is forecast, keeping the distribution tight around historical May norms and limiting the chance of extremes above 23°C or below 18°C. Updated model guidance released in the next 24–48 hours will likely narrow the range further before resolution.