Recent forecasts from multiple models converge on a daytime high near 22–23°C for Istanbul on September 26, consistent with seasonal norms and the market’s leading probabilities. A cool front and heavy rain on September 23 temporarily suppressed temperatures below average, but clearing skies and a building northeasterly flow are expected to allow moderate daytime warming without strong advection of cooler maritime air from the Black Sea. Key variables creating the tight spread among 20–24°C outcomes include the precise timing and extent of any residual cloud cover, which would reduce insolation and cap the maximum; local sea-breeze moderation from the Bosphorus and Marmara; and minor ensemble differences in boundary-layer mixing and wind speed. Official updates from the Turkish Meteorological Service and short-range model runs over the next 48 hours will refine these thresholds ahead of market resolution.