**Unusually dry atmospheric conditions prevailed across Seoul throughout September 2026, driving the market's near-certain consensus on totals below 75 mm.** Station data and NASA POWER-derived measurements recorded only trace amounts on most days, with isolated light events totaling roughly 40–50 mm for the month—far below the long-term September average of 140–160 mm. The absence of significant typhoon tracks or monsoon remnants, combined with persistent high-pressure dominance, suppressed convective activity and rainfall. The final 5–10 mm from late-month showers aligned with Korea Meteorological Administration forecasts but did not alter the low cumulative outcome. While minor revisions to official totals remain theoretically possible before formal reporting closes, current observational consensus strongly supports the market-implied odds.