Forecast uncertainty for July 17 stems primarily from the East Asian summer monsoon’s variable influence on Seoul, where cloud cover, rainfall timing, and nocturnal radiative cooling can shift overnight lows by several degrees. Current model consensus points to typical mid-July conditions with lows near 22–24 °C, yet the near-even split between the 28 °C+ and 18 °C-or-below outcomes reflects trader assessment of possible deviations: clearer, drier air masses could allow stronger cooling toward the lower threshold, while persistent humidity, weak winds, or warm advection might keep readings elevated. Historical July minimums average 22–23 °C, underscoring how modest changes in steering patterns or precipitation timing—key variables monitored by Korea Meteorological Administration updates—can swing the recorded low across market thresholds.