Recent official forecasts and observational data from the Korea Meteorological Administration and global models indicate overnight lows in Busan settling near 21–22 °C on September 18, driven by northeasterly flow, partly cloudy skies after daytime rain, and dew points around 17–19 °C. These conditions align with typical mid-September climatology for the region, where average minimums hover near 20 °C amid transitional autumn patterns. Market-implied odds heavily favor 21 °C because ensemble guidance shows limited cooling potential overnight, with no significant cold-air advection or clear-sky radiational effects expected to push readings lower. Minor spreads to 18–19 °C reflect residual uncertainty in localized urban heat-island influences or exact timing of clearing, while probabilities below 17 °C or above 22 °C remain negligible absent major forecast revisions. Updated model runs and KMA briefings through the evening will determine final resolution.