Busan’s coastal maritime climate, moderated by the East Sea, typically yields early-September overnight lows near 23–25°C amid seasonal transition from peak summer warmth. Current forecasts from multiple models show highs of 27–29°C on September 2 with 30–80% rain chances and variable winds, creating uncertainty in nocturnal radiative cooling and boundary-layer mixing that directly affects minimum temperatures. Cloud cover, humidity near 80%, and any weak frontal passages or sea-breeze effects could shift the low by 1–3°C either way, explaining the tightly matched market-implied odds around the 21–29°C thresholds. Updated model runs and official observations from the Korea Meteorological Administration will clarify resolution criteria before the overnight period.