Recent forecast guidance from multiple models points to a daily maximum near 26–27°C in Busan on September 23 under partly cloudy skies and light easterly flow, producing the tight clustering of market-implied odds around 27–28°C. Differentiation among these outcomes hinges on subtle variations in daytime insolation, the precise timing of any high-cloud increase, and weak southerly advection along the western flank of the North Pacific high; stronger ridging or clearer conditions could push readings toward 28–29°C, while increased marine influence or earlier cloud build-up would favor the lower end of that range. Late-September climatology places the long-term average high near 24–25°C, so the current setup reflects a modest extension of subtropical warmth before the seasonal transition accelerates. Updated model runs and morning observations on the 22nd and 23rd will refine these small but market-moving differences.