Trader consensus on Polymarket prices a 60.5% implied probability for Seoul's highest temperature reaching 18°C or higher on April 17, driven by an ongoing unseasonal mid-April heatwave fueled by a persistent high-pressure ridge ushering warm southerly winds across the Korean Peninsula. Recent observations from the Korea Meteorological Administration (KMA) confirm this anomaly, with Seoul logging 28°C highs on April 13—the year's hottest—and sustained above-average warmth through April 16 around 21-23°C under partly cloudy skies. KMA short-term forecasts and ensemble models project daytime highs of 17-19°C tomorrow amid light winds and low precipitation risk (under 50%), aligning with the clustering of odds at 18°C+ (60.5%) and 17°C (18.5%). A potential frontal boundary could introduce clouds and cap peaks near 16-17°C, with final KMA updates expected later today resolving remaining uncertainty. Historical April averages hover at 17°C, underscoring the current warm departure.