**October precipitation totals in Seoul exhibit substantial interannual variability around the long-term mean of approximately 52 mm, driven primarily by the frequency and intensity of cold frontal passages from the Asian continent and any late-season tropical cyclone influences.** This climatological range supports elevated market-implied odds on the 85 mm+ bin, as occasional heavier rain events from stalled fronts or typhoon remnants can produce outliers well above average, while drier outcomes remain plausible under stronger high-pressure dominance. With October marking the post-monsoon transition to cooler, less humid conditions, traders are weighting the potential for above-normal accumulations amid typical model spread in seasonal outlooks. No major large-scale drivers such as pronounced ENSO anomalies have emerged to shift expectations away from this historical distribution as the month begins.