**Persistent rain and extensive cloud cover associated with a northeast flow are expected to moderate overnight cooling in Busan on September 26, supporting market-implied odds favoring a minimum near 19°C.** Official Korea Meteorological Administration guidance and multiple forecast models indicate a daily low in the 16–20°C range, with the highest probabilities clustered around 19°C and 16–18°C. Persistent precipitation and high humidity limit radiative heat loss at night, while historical late-September climatology shows typical minima near 18–20°C. Any earlier clearing or stronger onshore flow could allow slightly lower readings, creating the close contest among the leading outcomes. Updated model runs and the next KMA briefing will be the primary near-term catalysts for shifts in trader sentiment.