Trader consensus on Polymarket favors a 15°C overnight low in Seoul on May 18 at 29.5% implied probability, reflecting the latest Korea Meteorological Administration (KMA) guidance and ECMWF/GFS ensemble means clustering around 14–16°C amid a persistent high-pressure ridge fostering clear skies and radiative cooling. Recent unseasonably warm daytime highs near 30–32°C over the past week have driven nightly minima into the low teens, as seen in prior days like May 14–17 forecasts showing 12–15°C lows. However, high uncertainty stems from model divergences on an approaching frontal system potentially increasing cloud cover and winds, elevating lows toward 16–18°C per some runs like AccuWeather's 18°C projection. Key variables include pre-dawn sky clarity and southerly flow strength; watch KMA's next short-term update and 00z model refreshes for repricing before resolution at the official Seoul station.