Trader consensus on Polymarket has locked in 100% implied probability for Seoul's lowest temperature on April 26 at 8°C or below at Incheon International Airport station, driven by the Korea Meteorological Administration's (KMA) latest short-term forecast projecting morning lows around 6–8°C amid clear skies and a stable high-pressure ridge. Recent cold air advection from the north, combined with light winds under 5 km/h and low humidity, promotes strong radiational cooling overnight, consistent with observed dips to 9°C on April 24–25 and typical late-April diurnal swings exceeding 15°C. KMA ensemble models show tight agreement, with no significant divergence. Realistic challenges include unexpected low-level clouds or a sudden southerly breeze raising lows to 9°C, though upper-air data suggests minimal risk; final station observations resolve the market tomorrow morning.