Korea Meteorological Administration observations confirm Seoul's highest temperature reached exactly 19°C on May 1, 2026, at the reference station, driving trader consensus to a 100% implied probability for this outcome amid negligible 0.1% odds for 20°C or higher. A persistent cool air mass over the Korean Peninsula suppressed diurnal heating under mostly cloudy skies, with short-range forecast models precisely capturing hourly peaks of 16–19°C and no significant wind or insolation to push beyond. Evening readings at nearby Incheon International Airport fell to 14.4°C by 22:00 KST, solidifying the daily maximum well before midnight resolution. While May climatological averages exceed 22°C, this atypical synoptic pattern minimized upside risk; only an unprecedented data revision or unforecast late surge—both highly improbable—could challenge the positioning.