Official meteorological observations from Istanbul stations, including Atatürk Airport, recorded a daily maximum of 17°C on October 14 amid widespread rain, northerly winds gusting to 40+ km/h, and high humidity near 90%, aligning precisely with the market's 100% consensus on that threshold. This outcome reflects verified surface data rather than models, consistent with seasonal cooling trends and the passage of a frontal system that suppressed daytime warming. While near-certain given completed observations, resolution could shift only if post-event quality control revises the official high due to station calibration or microclimate discrepancies across the urban area.