**Trader sentiment strongly favors a below-average total of under 75 mm of precipitation in Seoul for September 2026, reflected in the 73% market-implied probability.** Historical averages for the month range from 128–142 mm according to long-term records from the Korea Meteorological Administration and other climatological sources, with most rainfall typically concentrated in the first half before the East Asian monsoon fully retreats. As of mid-September 2026, early-month rainfall has been limited outside isolated events, and current conditions plus extended forecasts from regional models show predominantly dry, stable high-pressure patterns with minimal precipitation probability through the remainder of the month. This dry spell aligns with the seasonal transition to autumn, when steering patterns and reduced moisture transport sharply lower rainfall likelihood. The strong consensus around the lowest bin highlights how recent observational data and model runs have reinforced expectations of a notably drier-than-normal September, though any late-month typhoon influence or forecast shift could still alter totals.