Recent KMA short-range forecasts and ensemble model runs place Seoul/Incheon’s August 21 maximum near 29 °C, with cloud cover and scattered afternoon showers expected to moderate peak heating. This keeps the market tightly clustered around 27–29 °C because modest shifts in timing or extent of precipitation—driven by a weak frontal boundary and typical late-summer humidity—can easily add or subtract 1–2 °C from the daily high. Sea-breeze effects at the Incheon measurement site further compress the range, while historical August climatology shows highs declining from early-month peaks yet still variable day-to-day. Traders are therefore weighting the latest model consensus and any updated KMA guidance that could resolve lingering uncertainty before resolution.