**Trader sentiment for Seoul’s June 2026 precipitation reflects high uncertainty around the timing and strength of the East Asian monsoon (Jangma), with market-implied probabilities tightly clustered across the 100–160 mm+ range.** Historical climatology places the long-term average near 130–145 mm, driven by rising convective activity in early June followed by the monsoon front’s typical arrival in the central region around June 25–27. As of mid-June, the first half of the month has likely contributed a moderate share of rainfall under pre-monsoon conditions, leaving the second half—and especially any early or intense monsoon onset—to determine whether totals stay near or exceed the upper bins. Key scientific drivers include the northward migration of the monsoon front, moisture flux from the western Pacific, and the positioning of the subtropical high-pressure system, which can either suppress or enhance rainfall. If the front stalls or intensifies earlier than climatology, additional heavy episodes could push accumulations toward or above 160 mm; conversely, a delayed or weaker onset would favor the 110–130 mm bands. Recent forecasts and official statements from the Korea Meteorological Administration indicate no extreme early signals, keeping probabilities balanced rather than concentrated on any single outcome. Traders are therefore weighting both the baseline climatological expectation and the inherent variability of monsoon onset timing, which can shift totals by tens of millimeters in the final weeks.