Recent forecast model runs for Taipei indicate overnight lows near 23–24°C on September 18, shaped by persistent northeasterly flow, moderate humidity near 80–90%, and variable cloud cover that modulates radiative cooling. Traders assign roughly 40% implied probability to 20°C or below, reflecting uncertainty in how much clear-sky cooling versus residual cloud and light winds will occur before dawn. Historical September minima average around 25°C, so current conditions represent a modest departure driven by the seasonal monsoon pattern. Central Weather Administration updates and refined model ensembles expected overnight will likely clarify whether the minimum settles in the low or mid-20s.