Latest forecast models from sources including the National Weather Service equivalents and European centers point to a maximum of 20°C in Istanbul on October 4, driven by a persistent high-pressure system (around 1027–1028 hPa) and steady northeast winds of 15–30 km/h that limit daytime warming. Hourly guidance shows temperatures rising from overnight lows near 16°C to afternoon peaks of 19–20°C under mostly clear skies with minimal cloud cover. This aligns closely with the long-term October average high of 19.4°C and recent observations on October 3 showing similar mild, stable conditions. Market-implied probabilities favor 20°C over 19°C due to tight model agreement and low precipitation risk, though minor forecast revisions could shift outcomes within the narrow 18–21°C range.