Recent numerical weather prediction model runs, including GFS outputs, show Istanbul's September 30 maximum temperature most likely reaching 20–21°C under persistent cloud cover, northeasterly winds of 15–30 km/h, and periods of light rain or showers. These conditions limit daytime solar heating while mild maritime air advection from the Black Sea prevents significant cooling or warming. Market-implied odds align closely with this consensus, with the narrow spread between 20°C and 21°C reflecting minor differences in model timing of cloud breaks and precipitation intensity. Updated forecast guidance expected overnight will clarify whether the daily peak crosses the 21°C threshold.