**Trader sentiment for Seoul’s June 18 minimum temperature clusters around 19–21 °C because short-range forecasts consistently point to a daily low near 19–20 °C (67–68 °F).** Official guidance from sources such as timeanddate.com and the Korea Meteorological Administration shows overnight lows of roughly 19.4 °C under broken clouds, light winds, and moderate humidity (40–50 %), conditions that permit efficient radiative cooling after daytime highs near 33 °C. The tight spread among 21 °C (31.5 %), 20 °C (27 %), and 19 °C (23.5 %) reflects genuine forecast uncertainty: small differences in cloud cover, wind speed, or localized moisture can shift the minimum by 1–2 °C. Clearer skies or lighter winds would favor the lower end (19 °C), while increased cloudiness or a slight uptick in humidity would support 20–21 °C. Historical early-June climatology (typical lows 17–19 °C) and the approaching East Asian monsoon further anchor expectations in this narrow band, with minimal chance of extremes below 17 °C or above 22 °C given current model consensus.