Recent forecasts from multiple models indicate Istanbul's maximum temperature on September 13 will likely fall in the mid-20s Celsius range, driven by northerly flow, increasing cloud cover, and a modest chance of light showers that limit daytime heating. Ensemble guidance shows spread around 23–27°C, with historical September averages near 24–25°C providing context for typical variability under transitional autumn conditions. Trader positioning favoring 20–24°C outcomes reflects model uncertainty in exact peak timing, wind strength, and precipitation timing, as small shifts in steering patterns or insolation can alter the daily high by 2–3°C. Updated runs from agencies like the ECMWF and national meteorological services over the next 24–48 hours will refine these thresholds ahead of market resolution.