Traders assign nearly equal weight to sub-150 mm (45%) and 500 mm+ (44%) totals for Seoul in August 2026 because seasonal outlooks show near- or below-average rainfall amid high uncertainty. Historical August means hover near 348 mm, yet strong interannual variability arises from lingering East Asian monsoon moisture, atmospheric instability that favors sudden localized downpours, and the variable frequency or track of western North Pacific typhoons. Current Korea Meteorological Administration guidance highlights these convective risks without committing to totals near the climatological norm, leaving room for either suppressed monsoon flow or one or two intense systems to swing the month sharply drier or wetter.