Official forecasts from the Korea Meteorological Administration and supporting models indicate Busan’s September 18 maximum will reach 27 °C, driven by a warm, humid airmass with northeast winds near 10–15 km/h, limited daytime cloud cover after morning showers, and sea-surface temperatures supporting modest warming. Recent hourly observations climbing through the mid-20s °C align with this trajectory, while climatological norms for mid-September place typical highs around 25–26 °C. Trader consensus at 100 % implied probability for 27 °C reflects this tight model agreement and the absence of significant cooling mechanisms. A sudden increase in persistent rain or stronger onshore flow could cap temperatures below the threshold, though current guidance shows low probability of such shifts before sunset.