**Forecast models from agencies including the UK Met Office and regional ensembles project a daytime high of 15–17 °C for Istanbul on 15 October 2026.** Persistent northerly flow behind a cold front, combined with widespread showers and cloud cover, is suppressing temperatures below the early-October average near 20 °C. Multiple high-resolution runs show maxima clustered around 16 °C, with limited warming potential under the overcast, windy conditions. This scientific consensus—anchored in current observational data and short-range model agreement—directly supports the market’s heaviest positioning on 16 °C (49 %), followed by 15 °C (23 %) and 17 °C (20 %). Traders are pricing the narrow, rain-cooled range rather than any outlier warmer scenario.