Recent forecasts from multiple meteorological sources converge on a daytime high near 19–21°C for Istanbul on October 1, with the market’s tight split between 19°C and 20°C reflecting model consensus amid persistent cloud cover, light rain or drizzle, and northeasterly winds that limit daytime heating. Cooler maritime air advected from the Black Sea, combined with reduced solar insolation in early autumn and evaporative cooling from precipitation, keeps maxima close to the climatological average of roughly 19–20°C rather than allowing stronger warming. Any clearing skies or weaker winds in the final model runs could nudge readings toward the upper end of the favored range, while heavier or more prolonged rain would favor the lower side.