**Official forecasts from the Korea Meteorological Administration (KMA) and aligned reports project a daily maximum of 27°C for Incheon and Seoul on September 16, 2026, under clear skies, light easterly winds, and stable high pressure.** This consensus stems from consistent numerical weather prediction outputs showing daytime warming to that threshold without significant moisture or frontal influences, consistent with early-autumn climatology where typical highs range 24–28°C. Real-time observations at Incheon International Airport reached 27°C during afternoon hours, reinforcing the outcome. Trader positioning at 100% implied probability reflects high confidence in KMA-verified data as the resolution source. The primary uncertainty remains minor station-to-station variance or final-hour adjustments, though current synoptic conditions make deviations to 26°C or 28°C unlikely.