**Trader sentiment for Busan’s August 18 maximum temperature centers on 30–31 °C because official guidance and ensemble models cluster in that narrow band, with only modest upside risk to 32 °C.** Korea Meteorological Administration short-range forecasts and global models (GFS/ECMWF) project a typical mid-August pattern of warm, humid air under weak high pressure, tempered by possible passing showers and sea-breeze cooling along the coast. Historical climatology places Busan’s August daily highs near 29–30 °C, so the market’s slight tilt toward 31 °C reflects recent model runs that have trended a degree warmer amid above-average sea-surface temperatures in the Korea Strait. The 1 °C spread between the two leading outcomes hinges on subtle differences in cloud timing, precipitation efficiency, and boundary-layer mixing; even small increases in afternoon insolation or a delayed sea breeze can push the peak from 30 °C to 31 °C. With resolution less than 48 hours away, traders are weighting the latest KMA updates and model consensus most heavily while recognizing that a single revised run could still shift the final observed high by a degree.