Current forecasts for Busan point to a daily minimum near 19°C on September 23 under building high pressure, light northeast winds, and mostly clear to partly cloudy skies that favor moderate radiative cooling overnight. Trader sentiment remains split between a cold outcome (12°C or below) and a warm one (22°C or higher) because small shifts in cloud cover, wind speed, or residual warm advection from the south can swing the low by several degrees either way. Historical September averages place overnight lows around 19°C, so the market-implied odds capture genuine uncertainty in how quickly autumn cooling will assert itself versus lingering late-summer warmth. Updated model runs and Korea Meteorological Administration guidance over the next 48 hours will likely tighten the range.