**Forecast consensus for Busan on September 21 points to a minimum near 18–20°C under clear to mostly clear skies and moderate northeasterly flow.** Multiple models and agencies (including KMA-influenced outlooks, PredictWind, Met Office, and others) show overnight lows in this range, with daytime highs around 26–28°C and negligible precipitation risk. Primary drivers include a stable high-pressure ridge promoting radiative cooling overnight, tempered by Busan’s coastal location and persistent NE winds (typically 10–15 kt) that limit extreme drops by advecting slightly warmer marine air. No approaching fronts, typhoons, or significant cloud cover are indicated in the latest runs, keeping conditions typical for mid-to-late September climatology (average September lows near 19°C). Trader sentiment shows a near-even split between the 23°C+ outcome (47%) and 13°C or below (44.5%), with specific values clustered around 15–21°C also attracting interest. This reflects model spread and the inherent uncertainty in precise minimum-temperature resolution near the 18–20°C window, where small shifts in wind speed, cloud timing, or boundary-layer mixing can alter the low by 1–2°C. Upcoming model updates and any late adjustments to the high-pressure pattern will likely tighten these probabilities as the night progresses.