Recent meteorological observations and forecast models from agencies monitoring East Asian weather patterns indicate that Busan’s minimum temperature on September 15 will reach 20°C, driving the market’s near-certain consensus. Late-summer sea surface temperatures in the Korea Strait and prevailing southerly flow have maintained overnight lows near this level, consistent with climatological September averages for the coastal city. High-resolution numerical weather prediction ensembles show minimal spread around this threshold, with no significant cold advection or radiative cooling expected under the current stable high-pressure regime. A rapid shift in steering winds or an unforecasted marine layer could still alter readings by a degree or two before official verification closes the market.