Divergent short-range forecast models for Busan’s overnight minimum on September 27 create the tight market balance between warmer (25°C+) and cooler (15°C or below) outcomes. Recent ensemble runs show variability in cloud cover and northerly wind strength, which control radiative cooling rates after daytime highs near 24–26°C; clearer skies could push lows toward 18–19°C while increased moisture or breeze may hold them near 20–22°C. Historical late-September minima average around 19°C with a typical 2–3°C spread, underscoring why specific values like 19°C and 18°C attract the highest implied probabilities. Updated KMA and global model guidance expected within 48 hours will likely shift sentiment as resolution nears.