Official forecasts from the Korea Meteorological Administration and supporting models show a daytime maximum of 21°C in Incheon and Seoul on October 1, driven by clear skies, northwesterly flow, and cold-air advection behind a recent trough that dropped temperatures roughly 5°C from late September levels. This outcome matches the seasonal baseline near 21°C and aligns with observed peaks around 20–22°C across stations, producing near-certain market-implied odds. Minor model spread in wind or boundary-layer mixing could shift the precise reading by 1°C, but consensus data through evening hours support the 21°C threshold with high confidence.